Iran’s supreme leader warned on Tuesday that US attempts to depose his government would fail, as Washington and Tehran began indirect talks in Geneva on their long-running nuclear dispute amid a US military buildup in the Middle East.

Just a few hours after the negotiations began, Iran’s semi-official Fars news agency reported that parts of the strategic Strait of Hormuz will close for a few hours due to “security precautions” while Iran’s elite Revolutionary Guards conduct military drills in the world’s most vital oil export route.

Tehran has in the past threatened to shut down the strait to commercial shipping if it is attacked, a move that would choke off a fifth of global oil flows and drive up crude prices.

The US, which joined Israel in bombing Iran’s nuclear facilities in June, has deployed a battle force to the region, and US President Donald Trump has said “regime change” in Iran may be the best thing that can happen.

US envoys Steve Witkoff and Jared Kushner will take part in the negotiations, which are being mediated by Oman, a source briefed on the matter told Reuters, alongside Iranian Foreign Minister Abbas Araghchi.

US President Donald Trump said that he would be involved “indirectly” in the Geneva talks and that he believed Tehran wanted to make a deal.

“I don’t think they want the consequences of not making a deal,” Trump told reporters aboard Air Force One on Monday. “We could have had a deal instead of sending the B-2s in to knock out their nuclear potential. And we had to send the B-2s.”

US B-2 Bombers struck nuclear targets

Tehran knows that a previous attempt to revive talks was underway in June last year when Washington’s ally Israel launched a bombing campaign against Iran, and was then joined by US B-2 bombers that struck nuclear targets. Tehran has since said it has halted uranium enrichment activity.

A senior Iranian official told Reuters on Tuesday that the US’s seriousness on lifting sanctions on Iran and avoiding unrealistic demands are key to ensuring effective talks in Geneva.

The official, who declined to be named, said Tehran was coming to the negotiating table with “genuine and constructive proposals”.

The meeting took place at the residence of the Omani ambassador to the UN amid a heavy security presence. Some cars with Iranian diplomatic license plates were visible outside.

The US military is preparing for the possibility of weeks of operations against Iran if Trump orders an attack, two US officials told Reuters.

Iran itself began a military drill on Monday in the Strait of Hormuz, a vital international waterway and oil export route from Gulf Arab states, which have been appealing for diplomacy to end the dispute.

Benchmark Brent oil prices drifted lower in Asian trade on Tuesday as investors assessed the risk of supply disruption after Iran conducted the naval drills ahead of nuclear talks with the US.

Iran-US nuclear talks under shadow of protests and war

Tehran and Washington renewed negotiations on February 6 on their decades-long dispute.

Washington and its close ally Israel believe Iran aspires to build a nuclear weapon that could threaten Israel’s existence.

Iran says its nuclear programme is purely peaceful, even though it has enriched uranium far beyond the purity needed for power generation, and close to what is required for a bomb.

Since the June strikes, Iran’s Islamic rulers have been weakened by street protests, put down at a cost of thousands of lives, against a cost-of-living crisis driven in part by international sanctions that have strangled Iran’s oil income.

Unlike last time, the US has now placed what Trump calls a massive naval armada in the region.

Iran has joined the Nuclear Non-Proliferation Treaty, which guarantees countries the right to pursue civilian nuclear power in return for requiring them to forgo atomic weapons and cooperate with the UN nuclear watchdog, the International Atomic Energy Agency.

Israel, which has not signed the NPT, neither confirms nor denies having nuclear weaponry, under a decades-old ambiguity policy designed to deter surrounding enemies.

Scholars believe it does, having acquired the first bomb in 1966. Israeli journalists, circumscribed by military censorship, often refer cryptically to such capabilities or cite foreign media reporting on them.

Washington wants talks to include Missiles

Washington has sought to expand the scope of talks to non-nuclear issues such as Iran’s missile stockpile. Tehran says it is willing only to discuss curbs on its nuclear programme - in exchange for sanctions relief - and that it will not give up uranium enrichment completely or discuss its missile programme.

On Monday, US Secretary of State Marco Rubio told a news conference in Budapest that it was hard to do a deal with Iran, but the US was willing to try.

Iran’s Araqchi on Monday met Rafael Grossi, head of the IAEA in Geneva, to discuss cooperation with the nuclear watchdog and technical aspects of the impending talks with the US.

On Tuesday afternoon, Witkoff and Kushner will participate in three-way talks with Russia and Ukraine as Washington attempts to coax Ukraine and Russia into an agreement to end Moscow’s four-year-old invasion of Ukraine, the source said.