The first round of talks between high-ranking U.S. and Iranian officials in Switzerland ended Monday, mediators said, after a tense opening marked by Tehran’s announcement it had again closed the Strait of Hormuz and U.S. President Donald Trump repeating his threats to resume attacks on Iran, Reuters reports.

A joint statement from mediating nations Qatar and Pakistan said the ‌U.S. and Iran agreed to a roadmap toward a final deal within 60 days. Technical talks will continue for the rest of the week in the Qatari-owned Swiss mountain resort of Buergenstock, according to the statement, which was released by the Qatari foreign ministry.

The parties agreed to a mechanism to end the fighting in Lebanon and opened a communications line to help ensure safe passages for commercial ships through the contested strait, the statement said.

Talks in Switzerland made “encouraging progress,” Qatar and Pakistan added.

U.S. Vice President JD Vance began talks with Iranian officials on Sunday under the terms of a memorandum of understanding reached last week to extend a tenuous ceasefire from April for at least another 60 days. The discussions continued until the early hours of Monday.

In a post on social media, Iranian Foreign Minister Abbas Araqchi said his country had secured waivers for oil and petrochemical exports, the release of some frozen assets and the launch of a reconstruction and development plan for Iran.

Just before talks officially began on Sunday, Fox News reported that Trump said he told Iranian officials “you won’t have a country” if they tried to close the strait again. Trump also reiterated an earlier threat that the U.S. would take over the waterway and possibly charge a toll of its own, Fox News said.

Trump said he agreed to last week’s memorandum of understanding to avert a global economic depression from high oil prices caused by the strait’s closure. Oil prices had tumbled over the past week to levels unseen since the war started on February 28 with U.S.-Israeli attacks on Iran.

After the joint statement, Brent crude futures fell further, dropping more than $1 to $79.44 a barrel.

U.S. and Iranian sources provided separate accounts of the discussions in Switzerland.

Iran’s semi-official Tasnim news agency, citing an informed source, said that after Trump’s threats became public, the Iranian delegation refused to return to the room where talks were held, though messages were still being traded via Pakistani and Qatari mediators.

Iran, arguing that the U.S. had failed to meet its commitment to halt fighting in Lebanon, said on the weekend that it had again stopped maritime traffic through the strait and that Sunday’s talks would not cover substantive issues such as Iran’s nuclear programme.

At the talks in Switzerland, where U.S. and Iranian officials met in the presence of Qatari mediators, Vance played down the impact of violence in Lebanon, saying progress had been made towards ending hostilities there.

“These things are always a little bit messy,” he said.