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ZURICH/DUBAI/WASHINGTON, June 20 (Reuters) - A large Iranian delegation left for Switzerland on Saturday for talks with the United States, Iranian state media reported, while U.S. Vice President J.D. Vance indicated he would soon travel to meetings that Pakistan said would begin on Sunday.

Iranian media reported that the Iranian delegation is headed by chief negotiator Mohammad Baqer Qalibaf, and includes Foreign Minister Abbas Araqchi, as well as senior officials in the security and oil sectors and from the Central Bank.

Hours earlier, Iran’s Revolutionary Guard announced the closure of the Strait of Hormuz, a move that appears to increase risks ahead of talks as both sides seek to move forward with the interim agreement signed Wednesday by U.S. President Donald Trump and his Iranian counterpart Masoud Pezeshkian to end their nearly four-month-long war.

Iran's Revolutionary Guard warned ships against approaching the vital waterway for global oil and gas supplies, citing what it called Israeli "crimes" in Lebanon and a US violation of commitments aimed at maintaining the ceasefire. The Guard said ships would be at risk if they approached the strait.

But the US Central Command said 55 commercial vessels crossed the strait today, carrying large quantities of goods and more than 17 million barrels of oil to global markets.

The ceasefire in Lebanon, a condition of the interim agreement, appeared fragile amid an exchange of attacks between Israeli forces and the Iranian-backed Hezbollah group.

Momentum is increasing

Iranian Foreign Ministry spokesman Ismail Baghaei said Tehran will press Switzerland to ensure compliance with commitments, noting the other party's failure to honor agreements in the past.

Shortly before that, Fox News broadcast an interview with Vance in which he said he was confident that the ceasefire stipulated in Washington’s 14-point agreement with Tehran would hold, and that he saw no evidence of the Strait of Hormuz being closed.

Vance added, "I expect to leave sometime in the next couple of days, but you know that it always requires careful coordination and adherence to diplomatic protocols."

He stated that the American negotiators Jared Kushner and Steve Wittkopf were in Switzerland "for a few hours, to discuss some technical aspects of these negotiations."

He continued, "What I understood from my conversation with Jared and Steve this morning is that things are going well."

Reports of 20 killed in Lebanon

A cessation of fighting in Lebanon is a prerequisite for the start of 60 days of talks between the United States and Iran to resolve disputes over Iran's nuclear program and other issues.

The Lebanese Civil Defense reported that 20 people were killed in Israeli airstrikes on the country today, hours after the ceasefire took effect .

Israel said its strikes were in response to attacks by Hezbollah, while the Iranian-backed group declared it would not allow Israel "freedom of movement" in Lebanon.

Israel, which was not involved in the talks, says it is not a party to the agreement and will keep its forces in the Lebanese territory it currently controls.

A senior US official said the ceasefire in Lebanon went into effect around 4 p.m. (1300 GMT) on Friday. Sources from Hezbollah and Israel confirmed the agreement to Reuters.

Israeli Channel 12 reported that the Prime Minister and the Minister of Defense instructed the army to cease fire in Lebanon, but without withdrawing from the areas it had captured.

The National News Agency said that Israeli warplanes and drones bombed sites in southern Lebanon and the Bekaa Valley, both Hezbollah strongholds, on Saturday.

The Israeli military said Hezbollah fired more than 50 projectiles at Israeli forces in southern Lebanon overnight, and a senior military official said Israel responded by attacking what it described as Hezbollah targets.

A military statement said that Israel is committed to the ceasefire and will continue to respond to any threat to Israel or its forces.