LISBON, May 31 -- German Chancellor Angela Merkel and Portuguese Prime Minister Antonio Costa promised that Europe would contest the U.S. decision to impose import tariffs after a meeting here Thursday.

"If these tariffs really are imposed, we have a very clear position at the European Union (EU): we do not think such tariffs meet with World Trade Organization (WTO) rules," Merkel said.

"Of course we will respond and decide how to respond together," she added in comments made before U.S. president Donald Trump administration's decision to impose tariffs on European steel and aluminium imports had been confirmed.

Costa struck a similar tone. "The important thing is that Europe has a common trade policy and that we will not allow ourselves to be divided, as we've shown with Brexit," said Costa.

Merkel finished up a two-day visit to Portugal on Thursday by meeting Portuguese President Marcelo Rebelo de Sousa.

She also met Rui Rio, the leader of Portugal's main opposition party, the Social Democratic Party (PSD). Rio drew her attention to the EU's proposed budget for 2024 to 2027, which would likely mean Portugal losing out in terms of investment.

"She listened, she understood my argument, now we'll have to wait and see what effect it might have on negotiations," Rio said afterwards, as reported by the Lusa Portuguese News Agency.