WASHINGTON — President Trump’s top economic adviser said on Sunday that Mr. Trump had pulled out of a joint statement with allies at the Group of 7 meeting over the weekend because a “betrayal” by the Canadian prime minister had threatened to make Mr. Trump appear weak before his summit meeting on Tuesday with North Korea’s leader.

The adviser, Larry Kudlow, said that Mr. Trump had no choice but to take the action after the prime minister, Justin Trudeau, said in a news conference that Canada would not be bullied by the United States on trade.

Mr. Trump “is not going to let a Canadian prime minister push him around,” Mr. Kudlow said, adding, “He is not going to permit any show of weakness on a trip to negotiate with North Korea.”

Mr. Trudeau made his remarks, which were largely measured in tone, after the president had agreed to sign the joint statement and had left for his historic meeting with Kim Jong-un in Singapore. Negotiators had struggled to write a compromise communiqué addressing trade and other issues that the seven nations could agree on, but issued one on Saturday believing that there would be consensus.