China’s President Xi Jinping called on Tuesday for the national sovereignty of countries in West Asia and the Gulf to be “respected” as he outlined proposals for maintaining peace in the war-torn region.

US President Donald Trump has threatened to destroy any Iranian “fast attack ships” that approach the American naval blockade of Iranian ports that came into effect on Monday. Iran slammed the US blockade around its ports as a “grave violation” of its sovereignty. “The imposition of a maritime blockade constitutes a grave violation of the sovereignty and territorial integrity of the Islamic Republic of Iran,” Iran’s ambassador to the United Nations, Amir Saeid Iravani, wrote to UN Secretary General Antonio Guterres

Guterres on Monday called on “all parties” to respect freedom of navigation in the Strait of Hormuz, after Iran and subsequently the United States blocked passage through the critical waterway. Tehran and Washington are weighing in new in-person negotiations in a bid to reach a deal, and the talks could happen on Thursday, the Associated Press reported.

The report, quoting officials, said that discussions were still underway about a new round of talks, while a diplomat from one of the mediating countries went further to say Tehran and Washington have agreed to it. It’s unclear if the same level of delegation would be expected to attend.

US Vice President JD Vance on Tuesday morning said the talks stalled after Iran refused to accept American terms on refraining from developing a nuclear weapon. Vance told FOX News Channel’s “Special Report” that some progress was made on nuclear issues, but he felt Iran’s negotiators couldn’t make a deal without approval from Tehran. Iran has insisted its nuclear program is peaceful. However, it has pushed forward with steps that could give it the ability to build a nuclear weapon, including enriching uranium to near weapons-grade levels and developing long-range missiles potentially capable of delivering a bomb.

The ceasefire expires on April 22. The fighting has killed at least 3,000 people in Iran, 2,089 in Lebanon, 23 in Israel and more than a dozen in Gulf Arab states. Thirteen U.S. service members have been killed.