The United States expects talks with Iran to continue through the night in Switzerland, a US diplomat told reporters early Monday, as they work to permanently end the Middle East war.

The current round of negotiations got off to a rocky start, with the Islamic Republic’s delegation walking out in response to US President Donald Trump’s threats to strike Iran over its support for Hezbollah Sunday.

A US diplomat at the Swiss venue told reporters the Iranian delegation was involved in “robust discussions on all elements of the nuclear deal”, and gave clarifications on Iran’s messaging “on the Strait and building deconfliction mechanisms to ensure the Strait will remain fully open.”

The negotiations to end a war that sowed chaos across the region and rattled the global economy are meant to trigger a 60-day period to settle broader issues that have dogged US-Iranian relations for decades.

But disagreement over key sticking points and the threat of renewed fighting in Lebanon weighed on the talks, with Washington and Tehran exchanging threats in parallel with the negotiations.

“The delegation of the Islamic Republic of Iran, after meeting with the Qatari delegation as one of the mediating parties, left the building where the negotiations were being held”, Iran’s state news agency IRNA said.