International Monetary Fund chief Christine Lagarde led an attack by global economic organizations on U.S. President Donald Trump's "America first" trade policy on Monday, warning that clouds over the global economy "are getting darker by the day.

Trump backed out of a joint communique agreed by Group of Seven leaders in Canada over the weekend that mentioned the need for "free, fair and mutually beneficial trade" and the importance of fighting protectionism.

The U.S. president, who has imposed import tariffs on metals, is furious about the United States' large trade deficit with key allies. "Fair trade is now to be called fool trade if it is not reciprocal," he tweeted on Monday.