According to an Associated Press report on Sunday, Merkel says the three leaders "agreed that the United States ought not to take any trade measures against the European Union", which is "resolved to defend its interests within the multilateral trade framework".
The delegation to be led by Treasury Secretary Steven Mnuchin includes the Commerce Secretary Wilbur Ross and the US Trade Representative Robert Lighthizer.
A spokesperson for the British government added that leaders in the European Union are discussing "the vital importance of our steel and aluminium industries and their concern about the impact of U.S. tariffs" and they have "pledged to continue to work closely with the rest of the European Union and the United States administration with the aim of a permanent exemption from USA tariffs".
But Brussels has vowed to retaliate if it faces tariffs by putting punitive duties on American products ranging from industrial and agricultural items to flagship products such as jeans and motorbikes, peanut butter and bourbon. "We are patient, we are prepared and Labour Day will be full of labour for us", he said.
The EU's three largest economies - Germany, Britain and France - held crisis talks on Sunday and the French presidency said afterwards they had agreed "the EU must be ready to act" if Washington presses ahead with the tariffs.
If Trump does decide to impose tariffs, the European Union would react as a unit "in light of the developments in the coming days and weeks", Altmaier said.
And economists warn that using national security as a justification for trade measures opens the door for other countries to do the same. "The president has not made any decision yet", Mnuchin said in an interview on Fox Business Network. "I expect that there will be a decision quickly". The White House, the Commerce Department and the National Security Council did not respond to requests for comment before publication.
The uncertainty over steel tariffs isn't just causing unease among allies. South Korea also won a temporary exemption, which eventually became a long-term exemption after the progression of talks on the U.S. -Korea Free Trade Agreement (KORUS).
European leaders have argued that their countries shouldn't be held responsible for China's practices.