US Vice President Joe Biden hailed France's "decisive" intervention in Mali on Monday and joined President Francois Hollande in calling for UN peacekeepers to be quickly deployed to the country.

On the first visit by a top US official since President Barack Obama's inauguration last month, Biden also joined Hollande in vowing to keep up pressure on Iran over its nuclear programme.

"We agreed on the need to as quickly as reasonably possible establish the African-led international mission in Mali and as quickly as is prudent transition that mission to the United Nations," Biden said after a lunch meeting with Hollande.

Biden also praised France's "decisiveness" in intervening in Mali and the "competence and capability" of French military forces, whose lightning advance since January 11 drove Islamist militants from key cities in northern Mali they had seized last year.

"Your decisive action was not only in the interest of France but quite frankly the United States and everyone," Biden said.

"We also support the political process that France is leading to restore a democratic government in Mali," he added.

France is eager to pass the baton to some 8,000 African troops pledged for the UN-backed AFISMA force in Mali, which is deploying at a snail's pace, while the UN Security Council is speeding up planning for its own force.

For its part, Mali expressed some scepticism about transitioning to a peacekeeping force.

"Today we are fighting terrorism. The AFISMA is a support mission to Mali," Foreign Minister Tieman Coulibaly told AFP.

"If it were to be transformed into a peacekeeping force, you have to define between whom... Mali and the terrorists? No. Negotiations with terrorists are out of the question."

Biden arrived in Paris on Sunday from the Munich Security Conference in Germany and was to travel to London for talks on Tuesday with Prime Minister David Cameron.

In Munich, Biden warned Iran that opportunities for diplomacy to resolve the issue of its nuclear programme were limited and Hollande said the two agreed more pressure on Tehran was needed.

"Despite all efforts, Iran is still refusing to be transparent," Hollande said after the talks. "Therefore we will pressure it right to the end to ensure the negotiations succeed."

Iran on Sunday announced fresh talks with world powers on its nuclear drive and said it was open to an offer from the United States for two-way discussions if Washington's intention was "authentic".

Biden repeated that Washington is prepared for talks with Iran but said Washington and Paris agreed that despite unprecedented sanctions Tehran was showing no signs of compromise.

"We also share the view that there has been no real evidence of any movement thus far by the Iranians," Biden said.

Biden said he stressed to Hollande Washington's interest in the revival of Europe's stagnant economy, while the two agreed on the need for a balance between debt control and efforts to generate growth.

"Europe is our largest economic partner... The United States has a profound interest in Europe's success, in Europe secure in the foundations of its monetary union."

Ahead of his visit to London, Biden told The Times that both Britain and the European Union would suffer if Britain left the EU. Cameron said last month he planned to hold a referendum on Britain's EU membership.

"We believe the United Kingdom is stronger as a result of its membership. And we believe the EU is stronger with the UK's involvement. That's our view," Biden said.