President Donald Trump was paying tribute Saturday to the four Americans killed in a suicide bomb attack in Syria this week as he set off to Dover Air Force Base for the return of their remains. The trip was not listed on the presidents public schedule that was released Friday night, but he tweeted the news before his Saturday morning departure from the White House. "Will be leaving for Dover to be with the families of 4 very special people who lost their lives in service to our Country!" he wrote. Nineteen people including the four Americans were killed in a suicide bombing on a small restaurant in the flashpoint northern Syrian town of Manbij on Wednesday. The attack, claimed by ISIS, was the deadliest to hit US troops since they deployed to Syria in 2014. It came after Trumps shock announcement last month that he was ordering a full troop withdrawal from the country because the jihadists had been "largely defeated." The attack highlighted the threat still posed by ISIS despite Trumps assertion and could complicate that withdrawal plan. Some of his senior advisers have disagreed with the decision and have offered an evolving timetable for the removal of the approximately 2,000 US troops. The Pentagon has identified three of the four Americans killed: -Army Chief Warrant Officer 2 Jonathan R. Farmer, 37, of Boynton Beach, Florida, who was based at Fort Campbell, Kentucky. -Navy Chief Cryptologic Technician (Interpretive) Shannon M. Kent, 35, of Pine Plains, New York, and based at Fort Meade, Maryland. -civilian Scott A. Wirtz from St. Louis. The Pentagon hasnt identified the fourth casualty, a civilian contractor. Over the past month, Trump and others have appeared to adjust the Syria pullout timeline, and US officials have suggested it will likely take several months to safely withdraw American forces from Syria. In a Dec. 19 tweet announcing the withdrawal, Trump had said, "We have defeated ISIS in Syria, my only reason for being there during the Trump Presidency." He said the troops would begin coming home "now." That plan triggered immediate pushback from military leaders, including the resignation of Defense Secretary Jim Mattis. Manbij is the main town on the westernmost edge of Syrian territory held by the US-backed Syrian Kurds, running along the border with Turkey. Mixed Kurdish-Arab Syrian forces liberated Manbij from ISIS in 2016 with help from the US-led coalition. But Kurdish control of the town infuriated Turkey, which views the main US Kurdish ally, the YPG militia, as "terrorists" linked to Kurdish insurgents on its own soil. Trump reinforced his withdrawal decision during a meeting with about a half-dozen GOP senators late Wednesday at the White House.