Delegations from the United States, Iran and regional mediators have started talks in Burgenstock, Switzerland, with an aim to advance the Memorandum of Understanding signed between Washington and Tehran last week, with analysts saying that Lebanon constitutes the "greatest test" for the talks.

The high-level meeting is taking place amid renewed tensions over the Strait of Hormuz following conflicting accounts from Iran and the US, and with Tehran accusing Washington and Tel Aviv of truce violations amid continued violence in Lebanon. Israel and Hezbollah renewed their truce on Friday.

Qatari Foreign Ministry spokesman Majed Al-Ansari said on Sunday that the parties to the meeting in Switzerland had established technical groups to negotiate the terms of a final peace deal between Tehran and Washington, which is due within 60 days of negotiations.

READ MORE: Israeli strikes kill 15 in southern Lebanon despite ceasefire

Specialized technical groups have been formed to "negotiate the terms of a final agreement, which will cover all aspects of the memorandum of understanding", Al-Ansari told the Qatar News Agency.

Meanwhile, Iran's semi-official Tasnim news agency reported on Sunday that the country will not reopen the Strait of Hormuz if the war in Lebanon is not ended, citing a source close to the Iranian negotiating team.

The source warned that if Israel's "crimes" in Lebanon continue, and Lebanon's territorial integrity is not guaranteed, Iran will hold no negotiation on other issues.

The Iranian delegation, led by Parliament Speaker Mohammad Bagher Ghalibaf and Foreign Minister Abbas Araghchi, arrived in Switzerland on Saturday.

Speaking to the Islamic Republic News Agency, Iranian Foreign Ministry spokesman Esmaeil Baghaei said that the ongoing conflict in Lebanon between Israel and Hezbollah, frozen Iranian funds and the sale of the country's oil will top the agenda in talks with the US in Switzerland.

Trita Parsi, executive vice-president of the Quincy Institute for Responsible Statecraft, told Al Jazeera that "Lebanon has always been the greatest vulnerability to this deal because this is really crucial to the Iranians".

Ryan Costello, the policy director at the National Iranian American Council, also said Lebanon poses the "greatest test" for the ceasefire deal. "I would not be surprised at all if there is a breakdown in the broader negotiations," he was quoted as saying by Al Jazeera.

Prior to departing for Burgenstock, US Vice-President JD Vance said that success in Switzerland starts with establishing the structure of the negotiations, as US and Iranian officials begin the next phase of talks.

He said the focus will be on making progress on Iran's nuclear program and the Lebanon ceasefire, while technical teams remain on the ground to work through the details, Fox News reported.

Pakistani Prime Minister Shehbaz Sharif said in a post on social media platform X on Saturday that in his call with Saudi Crown Prince Mohammed bin Salman, they agreed that the next phase of negotiations "must remain anchored in a firm commitment to dialogue and diplomacy, along with vigilance against any attempts that could undermine the peace process".

ALSO READ: Iranian, US delegations in Switzerland for talks to end ME conflict

Sharif is also in Switzerland for the high-level meeting, along with Pakistan's Chief of Army Staff Field Marshal Syed Asim Munir.

Israeli airstrikes killed at least seven people and wounded one in eastern and southern Lebanon, Lebanon's National News Agency reported on Sunday. On Saturday, Israeli attacks killed 16 people and wounded 12 in Nabatieh district in the south of the country, Al Jazeera reported, citing the Lebanese Civil Defense agency.

An Israel Defense Forces soldier was killed during an alleged attack by Hezbollah on Saturday morning, The Times of Israel reported.

Xinhua contributed to this story.

Contact the writers at jan@chinadailyapac.com