Bloomberg - European diplomats drew a line in the sand this month, telling U.S. officials their bullying tactics wouldn�t help marshal support for President Donald Trump�s Iran policy.

The firm response came in a conference call in early January when a senior State Department official threatened European car makers would be hit with tariffs unless the European Union backed Trump�s hard line. Diplomats from Germany, France and the U.K. said that such tactics were completely unacceptable and would not help the president achieve his goals, according to U.S. and European officials familiar with the exchange.

The State Department team was struck by the firmness of the European line and passed their message on to the White House and officials from both sides noted the the U.S. administration dialed back the pressure on its European allies in the days that followed.

Brian Hook, the U.S.�s special representative for Iran, declined to comment when asked about the call. A spokesman for the White House wasn�t immediately available to comment.

The episode suggests a growing resolve among European officials to stand their ground as Trump looks to use trade policy to advance a widening range of U.S. geopolitical goals -- and it also shows their ability to pull together may survive the U.K.�s exit from the EU on Friday night.

Trump has been turning up the heat on Europe over a range of issues that also include relations with China and Russia. The president returned to the offensive later in the month when he targeted the EU for some of his harshest criticism at the World Economic Forum in Davos, Switzerland.

�They have trade barriers where you can�t trade, they have tariffs all over the place, they make it impossible,� Trump said a week later at the World Economic Forum in Davos, Switzerland. �They are frankly more difficult to do business with than China.�

The video conference around Jan. 8, first reported by the Washington Post, was led on the U.S. side by David Hale, the undersecretary for political affairs at the State Department, while the Europeans on the call were ambassadors, one of the officials said. By then European policy makers had already been planning for weeks to start formal action against Iran over its uranium enrichment violations.

A foreign ministry spokesman in Berlin declined to comment. His counterparts in London and Paris didn�t immediately reply to a request for comment.

EU-3 plans for a measured increase in pressure against Tehran were upended when the U.S. killed a top Iranian general in a drone attack at the start of January. That brought the two sides to the brink of war as Iran threaten widespread retaliation against U.S. targets.

The Europeans eventually triggered the dispute resolution of the Iran Nuclear Accord on Jan. 14, around a week after their clash with Hale. EU officials have insisted their decision was designed to force Iran to return to compliance with the accord, whereas Trump has called for the deal to be scrapped.

At the time of the drone strike, U.S. Secretary of State Michael Pompeo said EU allies weren�t �as helpful as I wish that they could be� in supporting the strike. EU officials, in turn, have blasted the American strategy of maximum pressure against Iran, with sanctions that have crippled the Iranian economy, as aimlessly aggressive and lacking a strategic objective.

� With assistance by Alex Morales