German Chancellor Angela Merkel said in a television interview on Sunday that the summit is a "sobering" and "depressing" experience with an outcome that "wasn't a great thing".
Mr Kudlow suggested Mr Trump saw Mr Trudeau as trying to weaken his hand before that meeting, saying the president will not "let a Canadian prime minister push him around ..."
China and the U.S. have averted a trade war by reaching an agreement last month under which Beijing has agreed to "significantly increase" its purchases of American goods and services to reduce $375 billion trade deficit with Washington.
Key to Trump's concerns appeared to be declarations on trade, a thorny issue following Trump's announcement that he planned to impose tariffs on steel and aluminum exports from the European Union, Canada and Mexico. "The Prime Minister said nothing he hasn't said before - both in public, and in private conversations with the president".
"There are still good reasons to continue our fight [aimed at keeping close transatlantic partnership], even though we can not just rely on it anymore", she added.
"The communique was agreed by all the parties who attended the G7 and we fully intend to honour it", the spokesman said.
"That's what matters", he wrote.
Finnish Prime Minister Juha Sipila said Sunday that the rift between G7 members at the summit reflects the unpredictability in global political arena, and he hoped the aftermath of the summit would be cleared up quickly.
"International cooperation can't depend on anger and small words".
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The spat drew in Germany and France, which sharply criticised Trump's decision to abruptly withdraw his support for a Group of Seven communique hammered out at the Canadian summit on Saturday, accusing him of destroying trust and acting inconsistently.
The G-7 summit was coming down to the wire.
Officials from European delegations quickly leaked copies of the joint statement, and it was published online moments before Trump tweeted.
Trump told Macron during their meeting in Washington that there are too many German cars in the United States, the source previously told CNN. "And I think we should have a reciprocal tax", the U.S. president said.
"We spent two days to obtain a text and commitments".
"We commit to modernize the WTO to make it more fair as soon as possible". And he said, "I just want to inform you that we have reduced it to 75, but we have further reduced it to 50".
But Trump had already said he would not hesitate to shut countries out of the United States market if they retaliate against his tariffs. "They know it", he insisted in his departing news conference. I believe that. John McCain believes it. there's a movement all over the world to look inward, not outward, and I think it's a mistake.
"It's actually not a real surprise".
"The U.S. pays close to the entire cost of North Atlantic Treaty Organisation - protecting many of these same countries that rip us off on trade (they pay only a fraction of the cost - and laugh!)", he tweeted. "Not fair to the PEOPLE of America!"
The US has said that the best way to solve trade disputes was by lowering tariff and non-tariff barriers by countries and allowing the free market to operate.