On March 16, the Crimean authorities held a referendum on Crimea's annexation to Russia. Crimea's union with Russia was allegedly approved by 96.77% of those voting, with a turnout of 83.1%. Ukraine, the United States, the European Union, and other countries denounced the referendum as illegal and not held in a free or fair manner. President Putin signed a "treaty" with Crimean leaders on March 18 formally incorporating Crimea into Russia. This move was also denounced by Ukraine, the United States, the EU and other countries as a blatant violation of Ukraine's sovereignty and territorial integrity and a violation of international law. Until March 18, the Russian takeover of Crimea had been achieved with no bloodshed with the Ukrainian government forces on the peninsula, even in cases where Russian troops forcibly seized Ukrainian installations. However, on that day one Ukrainian soldier was killed when Russian forces stormed a Ukrainian base in Simferopol. On March 24, Ukraine announced that it would withdraw its remaining military personnel from Crimea, due to threats against them and their families made by Russian forces. On March 28, Russian Defense Minister Sergei Shoigu said that military installations in Crimea were under its control and that all Ukrainian troops that remained loyal to Ukraine had left the peninsula. On March 17, the Administration announced visa bans and asset freezes against several senior figures from Russia and the secessionist Crimean government. On March 16 and 20, after Russia moved to annex Crimea, the Administration issued two additional Executive Orders expanding the scope of sanctions. They permit the Administration to freeze the assets of persons working in key areas of the Russian economy, including "financial services, energy, metals and mining, engineering, and defense and related materiel" (see also below, " U.S.-Russia Relations after the Occupation and Annexation of Crimea "). On March 18, 2014, President Putin signed a treaty with Crimea annexing the region, and that same day presented it to the Russian Federal Assembly (legislature) for ratification, along with a bill changing the constitution to add Crimea and Sevastopol as federal units of Russia. A speech he delivered was viewed by many observers as reprising themes he and other officials made over the last few weeks of the crisis, and as indicative of his thinking and grievances. He emphasized the long history of Russian domination over Ukraine, but as depicted in Soviet historiography on nationality issues, viewed the relationship as beneficial to both Russians and Ukrainians. He did not distinguish between Ukrainian and Russian national identity, asserting that both nations were "one people, we cannot live without each other." He stressed that "Crimea has always been an inseparable part of Russia." He stated that in Ukraine in early 2014, "nationalists, neo-Nazis, and anti-Semites ... resorted to terror, murder, and riots," leading to a coup. He asserted that "these ideological heirs of Bandera, Hitler's accomplice during World War II," were Russo-phobes aiming to repress Russian-speakers in Crimea. Russia created conditions for Crimeans to freely vote on their future for the first time in history, he claimed. He asserted that the Crimean region of Ukraine had the same right as Ukraine itself took in 1991 to self-determination, and also averred that since Kosovo Albanians were encouraged by the United States and the West to claim independence, then Russians, Ukrainians, and Crimean Tatars could do the same. In a second part of his speech, President Putin outlined what he viewed as a long history of U.S. and Western abuses against Russia. He asserted that what he viewed as the orchestration of a coup in Ukraine had finally "crossed the line," that Russia had been backed into a corner from which it could not retreat, and that an overwound spring would "snap back hard." Ticking off grievances, he depicted the world since the collapse of the Soviet Union as unstable, with the United States sweeping aside international law and "ruling by the gun," believing in its own exceptionalism to unilaterally decide the destiny of the world. The United States acts as it pleases, he asserted, either forcing international organizations to approve its actions or ignoring them, as it did in Yugoslavia, Afghanistan, and Iraq. He also appeared to identify the United States as orchestrating "color revolutions" in other countries to impose standards that violate the way of life, traditions, and culture of the peoples of those countries, leading to chaos and violence, and the "Arab Winter." Such "color revolutions" have been aimed at Ukraine and Russia and against Eurasian integration, he asserted. He claimed that Russia had to act to prevent NATO from taking over Crimea and threatening southern Russia. He termed the protection of Russian-speakers a priority of all Russians and hence a foundation principle of foreign policy. He depicted those in Russia who might object to the annexation as "national traitors" manipulated by the West, and argued that 95% of Russian citizens and the great majority of Crimeans support the annexation of the region. On March 20, the State Duma (lower legislative chamber) almost unanimously approved the annexation treaty and the constitutional changes. The next day, the Federation Council (upper legislative chamber) unanimously gave its approval. Putin signed the bill into law and the federal changes became part of the constitution. He immediately appointed a presidential representative to administer the new federal district. On March 27, 2014, the U.N. General Assembly approved a resolution by the vote of 100-11, with 58 abstentions, affirming Ukraine's territorial integrity and terming the March 16 referendum in Crimea illegitimate and not a basis for a change in the status of the region. Russia's U.N. ambassador Vitaly Churkin argued that Russia could not ignore the right of Crimeans to self-determination and that Crimea had been "re-unified" with Russia. Armenia and Belarus joined Russia in voting against the resolution, while Azerbaijan, Georgia, and Moldova voted for it. Among other Soviet successor states that attended the session, Kazakhstan and Uzbekistan abstained. China, Afghanistan, and Pakistan also abstained. Kyrgyzstan, Tajikistan, and Turkmenistan did not participate in the vote. In late March 2014, President Obama expressed concern about the build-up of Russian forces on Ukrainian's borders and called for their pullback. Press reports citing unnamed U.S. intelligence officials put their number at about 30,000, although the Secretary of Ukraine's National Security and Defense Council has estimated them at about 100,000. Although Russia may not be as central to U.S. interests as was the Soviet Union, engagement between the two is essential in many areas. Russia remains a nuclear superpower. It still has a major impact on U.S. national security interests in Europe, the Middle East, and Asia. Russia has an important role in the future of arms control, the nonproliferation of weapons of mass destruction (WMD), and the fight against terrorism. U.S.-Russia relations have faced severe challenges posed by Russian foreign behavior, including in Georgia in August 2008 and Ukraine in February-March 2014. Russia is a potentially important trading partner. Russia is the only country in the world with a greater range and scope of natural resources than the United States, including oil and gas reserves. It is the world's second-largest producer and exporter of oil (after Saudi Arabia) and the world's largest exporter of natural gas. It has a large, relatively well-educated labor force and scientific establishment. Also, many of Russia's needs—food and food processing, oil and gas extraction technology, computers, communications, transportation, and investment capital—are in areas in which the United States is highly competitive, although bilateral trade remains relatively low. Russia is a multi-ethnic state with over 100 nationalities and a complex federal structure inherited from the Soviet period that includes regions, republics, territories, and other subunits. During Boris Yeltsin's presidency, many of the republics and regions won greater autonomy. Only the Chechen Republic, however, tried to assert complete independence. President Putin reversed this trend and rebuilt the strength of the central government vis-à-vis the regions. In coming decades, the percentage of ethnic Russians is expected to decline because of relatively greater birthrates among non-Russian groups and in-migration by non-Russians. In many of Russia's ethnic-based republics and autonomous regions, ethnic Russians are becoming a declining share of the population, resulting in the titular nationalities becoming the majority populations. Implications may include changes in domestic and foreign policies under the influence of previously marginalized ethnic groups, including the revitalization of Yeltsin-era moves toward federal devolution. Alternatively, an authoritarian Russian central government that carries out chauvinist policies could contribute to rising ethnic conflict and even separatism. The Russian Constitution combines elements of the U.S., French, and German systems, but with an even stronger presidency. Among its more distinctive features are the ease with which the president can dissolve the legislature and call for new elections and the obstacles preventing the legislature from dismissing the government in a vote of no confidence. The president, with the legislature's approval, appoints a prime minister, who heads the government. The president and prime minister appoint government ministers and other officials. The prime minister and government are accountable to the president rather than the legislature. The bicameral legislature is called the Federal Assembly. The State Duma, the more powerful chamber, has 450 seats. In July 2005, a law was passed that all 450 Duma seats would be filled by means of party list elections, with a 7% threshold for party representation.