The cruise-missile strikes on the Syrian Shayrat Airbase, conducted by the U.S. on April 7, 2017 as a response to the Khan Shaykhun chemical attack, were condemned by Russia as an "act of aggression" that was based on a "trumped-up pretext", which substantially impaired Russia–United States relations. Russian prime minister Dmitry Medvedev said the attack had placed the U.S. on the cusp of warfare with Russia. Both Donald Trump in April and the Russian government in May characterised the relationship between the countries as frozen and lacking any progress; in early June, Vladimir Putin said relations were at an all-time low since the end of the Cold War. In mid-June 2017, the Russian foreign ministry confirmed that, for the first time ever, Russia had failed to receive a formal greeting from the U.S. government on occasion of Russia's national day celebrated on June 12.