Despite the Sunshine Policy and efforts at reconciliation, the progress was complicated by North Korean missile tests in 1993, 1998, 2006, 2009, and 2013. By early 2009, relationships between North and South Korea were very tense; North Korea had been reported to have deployed missiles, ended its former agreements with South Korea, and threatened South Korea and the United States not to interfere with a satellite launch it had planned. North and South Korea are still technically at war (having never signed a peace treaty after the Korean War) and share the world's most heavily fortified border. On 27 May 2009, North Korean media declared that the Armistice is no longer valid because of the South Korean government's pledge to "definitely join" the Proliferation Security Initiative. To further complicate and intensify strains between the two nations, the sinking of the South Korean warship Cheonan in March 2010, is affirmed by the South Korean government to have been caused by a North Korean torpedo, which the North denies. President Lee Myung-bak declared in May 2010 that Seoul would cut all trade with North Korea as part of measures primarily aimed at striking back at North Korea diplomatically and financially, except for the joint Kaesong Industrial Project, and humanitarian aid. North Korea initially threatened to sever all ties, to completely abrogate the previous pact of non-aggression, and to expel all South Koreans from a joint industrial zone in Kaesong, but backtracked on its threats and decided to continue its ties with South Korea. Despite the continuing ties, Kaesong industrial zone has seen a large decrease in investment and manpower as a result of this military conflict. In February 2016, the Kaesong complex was closed by Seoul in reaction to North Korea's launch of a rocket earlier in the month unanimously condemned by the United Nations security council.