President Donald Trump on Wednesday said the United States and the European Union had launched a "new phase" in their relationship, saying that the two major economies would start negotiations immediately on a number of areas that include working toward "zero tariffs" on industrial goods, and further cooperation on energy issues.

"We agreed today, first of all, to work together towards zero tariffs, zero non-tariff barriers and zero subsidies for the non-auto industrial goods," Trump said at a joint press conference in the White House Rose Garden with European Commission President Jean-Claude Juncker.

Trump did not address whether the two leaders had reached an agreement on car tariffs, though Juncker said that no new tariffs would be assessed as negotiations proceed. Economists have said that, among the major issues under discussion, tariffs on cars could be the biggest threat to the U.S. economy.

Juncker said the two leaders also agreed that as long as negotiations were ongoing, "we'll hold off further tariffs and reassess existing tariffs on steel and aluminum" put in place by the Trump administration. "This was a good, constructive meeting," he added.

Key details of the agreement were still unclear late Wednesday afternoon, but a deal not to impose further tariffs while negotiations are underway would avert a trade war between the United States and Europe. It would also represent a victory for the European Union, which had been bracing for new automobile tariffs as high as 25%.

“All things considered it could have been a hell of a lot worse. They agreed to keep talking. Considering how bellicose Trump was when he said ‘tariffs are great.’ I think this was the best outcome you could have hoped for,” said Greg Valliere, global strategist at Horizon Investments. “The reaction from Republicans on Capitol Hill has been so hostile to Trump’s tariff proposal, that that maybe was a factor in them agreeing to keep talking.”