US Vice President JD Vance on Sunday said President Donald Trump had asked his team to "turn over a new leaf" in relations with the Iranian people, expressing optimism as technical negotiations between Washington and Tehran got underway in Switzerland.

Speaking at the start of the talks, Vance said the discussions may not resolve every disagreement between the two sides, but would mark a historic step forward.

"The technical negotiations may not solve every disagreement, but it will allow us to sit together as teams for the first time in history," Vance said.

"Trump is committed to see a full regional ceasefire," he said, while acknowledging that "these kinds of ceasefires are always a little bit messy."

The vice president said Washington had seen encouraging signs in recent days, particularly in Lebanon.

"We've seen great progress over the last couple of days in ensuring the ceasefire in Lebanon holds," he said, adding that the U.S. had also made "great progress in the last few hours."

While describing Iran as "a driver of regional instability," Vance said the objective of the talks was to use diplomacy to reshape relations across the Middle East.

"What we're trying to accomplish is through diplomacy to work together and transform the Middle East," he said.

Vance said Trump had directed his team to seek a fresh start with Iran's people and build a more stable future for the region. Again, US and Iranian negotiators held a trilateral meeting with Qatari mediators as part of talks in Switzerland, officials with knowledge of the situation told Reuters on Sunday.