US Vice President JD Vance said on Sunday that Europe was "an important ally" despite disagreements over trade, as he met European Commission President Ursula von der Leyen in Rome after the new pope's inauguration mass.

The talks were the first at such a high level since US President Donald Trump introduced his sweeping tariffs this year.

At the start of the meeting, Vance said he hoped the talks "will be the beginning of some long-term trade negotiations".

"I've said repeatedly that I think Europe is an important ally of the United States," he said.

"But of course we have some disagreements, as friends sometimes do, on issues like trade, and we also have many agreements and many things that we can work on together, and I'm looking forward to this conversation."

For her part, von der Leyen -- who sat on one side of Italian Prime Minister Giorgia Meloni at her office in Rome -- hailed the "very special and close relationship" between the US and the European Union.

"Everybody knows that the devil is in the detail, but what unites us is that at the end we want, together, to have a good deal for both sides," the EU chief said.

In April, Trump announced a 20-percent tariff on most EU goods, along with higher duties on dozens of other nations, but has since frozen the measure until July.

The US president said on May 9 that he hoped to meet the "fantastic" von der Leyen, saying that the bloc wanted to "make a deal very badly" with the US. (AFP)