Later, White House spokeswoman Sarah Sanders, who was traveling with the president, issued a statement that said Kudlow's doctors said he had a "very mild heart attack". He previously served in the Reagan administration and emerged as a leading evangelist for tax cuts and smaller government.
"It was a betrayal", Kudlow told Tapper of Trudeau having said in the news conference Saturday that Canada will "move forward with retaliatory measures" on July 1 in response to the Trump administration's decision to impose tariffs on steel and aluminum imports from Canada, the European Union and Mexico.
On Sunday, Kudlow said Canadian Prime Minister Justin Trudeau had stabbed Trump "in the back" by criticizing the White House's trade agenda after the president left for Singapore.
Larry Kudlow Has Suffered a Heart Attack
The former conservative commentator, whom Trump named to lead the National Economic Council in March, was sent to Walter Reed Medical Center in Washington, D.C. "He made an error", Kudlow said.
Kudlow had joined Trump at the contentious G-7 at the end of last week. He recently returned from the G-7 summit in Canada, where Trump found himself at odds with US allies over his decision to impose steel and aluminum tariffs.
Kudlow was admitted to Walter Reed Medical Center, according to Trump.
Mr. Trump hired him in April to replace Gary Cohn as the head of the National Economic Council, reportedly because he enjoyed Mr. Kudlow's combative television appearances. He was a CNBC contributor before returning to the White House this year.
Associated Press writers Zeke Miller in Singapore and Jill Colvin in Washington contributed reporting.