After the chemical attack on Khan Shaykhun, warships of the U.S. Navy launched 59 Tomahawk missiles at the Syrian Ba'athist government's Shayrat Air Base which was said to be the source of the chemical attack. The American attack, taking place on 7 April 2017, was the first officially announced deliberate attack on Syrian Ba'athist government forces. Due to being launched without authorisation from Congress or the UN Security Council, the strike triggered an emergency UNSC meeting. Russian President Putin viewed the U.S. attack as "an act of aggression against a sovereign country violating the norms of international law". The U.S. representative responded that "the moral stain of the Assad regime could no longer go unanswered." American forces struck the Syrian military again on 18 May, when a Syrian army convoy advancing in the vicinity of the border town of al-Tanf, which hosted a US-controlled airbase, came under attack by US fighter jets. Nevertheless, the Syrian Ba'athist government's desert offensive continued and on 9 June Ba'athist government forces secured a part of Syrian–Iraqi border for the first time since 2015.