President Trump tweeted Sunday night from Singapore attacking U.S. allies over the trade deficit.
His tweets came after he left early from a divisive G7 meeting in Canada.
"Fair trade is now to be called fool trade if it is not reciprocal," said Trump, ahead of his summit with North Korean leader Kim Jong Un.
"Not fair to the people of America! $800 billion trade deficit," he said. "Why should I, as president of the United State, allow countries to continue to make massive trade surpluses, as they have for decades, while our farmers, workers & taxpayers have such a big and unfair price to pay?"
Trump also attacked fellow members of the North Atlantic Treaty Organization (NATO) for paying disproportionately less than the United States to maintain the Western alliance, according to Reuters.
"Germany pays 1 percent (slowly) of GDP towards NATO, while we pay 4 percent of a much larger GDP. Does anybody believe that makes sense?"
"We protect Europe (which is good) at great financial loss, and then get unfairly clobbered on trade. Change is coming!"
Trump also renewed attacks on Canadian Prime Minister Justin Trudeau, who had hosted the G7 meeting in Quebec.
Trump's supporters also criticized Trudeau.
Trade adviser Peter Navarro told "Fox News Sunday" that "there is a special place in hell for any leader that engages in bad faith diplomacy" with Trump.