President Donald Trump canceled a planned trip this weekend to South America where he was to participate in a summit with other Western Hemisphere leaders, the White House said, as he contemplates a military response to a chemical weapons attack in Syria.

“President Trump will not attend the 8th Summit of the Americas in Lima, Peru or travel to Bogota, Colombia as originally scheduled,” Press Secretary Sarah Huckabee Sanders said Tuesday in a statement. “At the President’s request, the Vice President will travel in his stead. The President will remain in the United States to oversee the American response to Syria and to monitor developments around the world.”

The White House had already scaled back the trip in recent weeks, and one planned meeting with Peru’s president was canceled after he resigned amid corruption allegations.

Trump said late Monday that the U.S. will respond “forcefully” to a suspected chemical weapons attack by Syrian President Bashar al-Assad’s regime over the weekend, after suggesting earlier that Russian President Vladimir Putin may share responsibility. He would not describe the U.S. response or say when it would come. “I don’t like talking about timing,” he said.

The development also comes a day after the FBI raided the office of Trump’s personal lawyer, Michael Cohen, based on information gathered in Special Counsel Robert Mueller’s investigation of Russian interference in the 2016 election. That news caused Trump to lash out at Mueller to reporters late Monday, describing the raid as a criminal act and an “attack on our country.”

Some of Trump’s allies encouraged him to respond by firing Mueller, FBI Director Christopher Wray or Deputy Attorney General Rod Rosenstein, who is supervising Mueller’s probe and approved the raid. Trump entertained a question about firing Mueller while speaking with reporters, but did not say whether he was considering the move.

Tensions in the Middle East escalated even higher early Monday with an airstrike by unknown warplanes against a Syrian airbase. Russia blamed Israel for the raid; Israel hewed to its customary no-comment policy.