European Commission President Jean-Claude Juncker called on Thursday for clarity from Donald Trump on issues such as global trade, climate policy and future relations with NATO allies following his U.S. victory in the presidential election.

During the election campaign, Trump, a billionaire businessman who has never held public office, strongly criticized free trade, NATO and policies designed to halt global warming, rattling Washington's allies and trade partners.

"We would like to know how things will proceed with global trade policy," Juncker said at a business event in Berlin.

"We would like to know what intentions he has regarding the (NATO) alliance. We must know what climate policies he intends to pursue. This must be cleared up in the next few months."

Juncker said he did not expect the trade deal between the United States and the European Union, currently being negotiated, to be finalised this year as previously planned.

"The trade deal with the United States, I do not view that as something that would happen in the next two years," he said.

Juncker, speaking in the German capital, also said on Thursday the EU's Stability and Growth Pact which sets rules on reducing public debt and budget deficits had to be flexible.

"Flexibility does not mean a departure for stability but an intelligent application of our common system of rules," he said.

Juncker said he understood Italy's position after the Commission forecast on Wednesday that Rome would break EU rules on budget deficit and public debt reduction this year and next.

Rome says the higher structural deficit is due to extraordinary spending on migration and post-earthquake reconstruction.

Juncker had said on Wednesday that the Commission must judge a country according to its problems and that in this situation the EU's place was "at Italy's side and not against it".

Juncker urged restraint in criticism of the European Central Bank’s monetary policy and accused German politicians - many of whom frequently make verbal attacks on the bank's ultra-loose monetary policy - of applying double standards.

Juncker said former German finance minister Theo Waigel had in the 1990s told other EU states not to criticize the bank.

"Now, the European Central Bank is not exactly doing what many Germans want and now criticism of the ECB is allowed," Juncker said. "I’m in favor of discussing monetary policy in an argumentative manner, but this cannot happen depending on how one feels. This has to be consistent."

Addressing the rise of euroscepticism across the EU that was highlighted by Britain's vote in June to leave the bloc, Juncker said the European Commission had in the past "stuck its nose" into too many details of people's lives.

"There is now a draft for an EU directive, which I stopped, about the height of heels of female hairdressers all over Europe," Juncker said. "So I stopped that and now I have a row with the European labor unions."