The United States said "the ball is in the Iranian court" on ending the Middle East war, as diplomats accelerated efforts on Tuesday towards a new round of peace talks after weekend negotiations failed to produce a deal.
US Vice President JD Vance had left talks hosted by Pakistan on Sunday, saying he had handed Tehran the "final and best offer".
Iran has blamed Washington for making maximalist demands, but its leaders have in the last hours not dismissed efforts by world leaders to get both sides back to the negotiating table.
Crucially, a fragile two-week truce agreed last Wednesday to give time to find a lasting ceasefire remained in place, even though a US naval blockade of Iranian ports began at the Strait of Hormuz, which had been effectively closed by Tehran.
The standoff at the strait, through which one-fifth of global oil transits, failed to dampen optimism at global markets, with Asian equities rallying while oil continued a downward slide.
President Donald Trump insisted Iranian representatives had called Washington since a US delegation returned empty-handed from negotiations in Islamabad.
"I can tell you that we've been called by the other side. They'd like to make a deal. Very badly, very badly," Trump told reporters outside the Oval Office.
Diplomatic efforts were also accelerating elsewhere, with Russian Foreign Minister Sergei Lavrov landing in Beijing on Tuesday, hours after Iran's state news agency reported that he had spoken about the crisis in a phone call with his Iranian counterpart Abbas Abbas Araghchi.
Moscow has offered to hold Iran's enriched uranium safely as part of any deal.
Trump has insisted that an agreement must include stopping Iran from ever getting its hands on a nuclear weapon, having launched the war under the pretext that Tehran was developing an atomic bomb -- which it denies.
During weekend talks, the United States reportedly sought a 20-year suspension of Iran's uranium enrichment program, according to media reports on Monday.
Iran in turn proposed to suspend its nuclear activity for five years, which US officials rejected, according to The New York Times.
- 'Full efforts' underway -
Pakistan's Prime Minister Shehbaz Sharif said on Monday that "full efforts are underway" to reach an agreement to stop the fighting and that US-Iran ceasefire was "holding".
Iranian state TV reported on Monday that Tehran "will continue to talk only within the framework of international law" in a phone call to his French counterpart Emmanuel Macron.
"We have clearly announced the terms of the ceasefire and we will adhere to it," Pezeshkian said, according to IRIB.
"I really think the ball is in the Iranian court, because we put a lot on the table. We actually made very clear what our red lines were," Vance said in an interview with Fox News on Monday.
Washington has "no flexibility" on US control of Iran's enriched uranium, and a verification mechanism to ensure it does not develop a nuclear weapon in the future.
"It's one thing for the Iranians to say that they're not going to have a nuclear weapon. It's another thing for us to put in place the mechanism to ensure that's not going to happen," Vance said.
Meanwhile, Araghchi blamed the United States for the impasse in the talks. "Unfortunately, we witnessed the continued excessive demands of the American side in the negotiations, which led to the failure to achieve a result," his ministry quoted him as saying.
- Freedom of navigation -
The push for new talks came as a US naval blockade began around Iranian ports, an action announced by Trump on Sunday and slammed by Iran as a "grave violation of its sovereignty".
Iran had already closed the Strait of Hormuz to what it regards as enemy shipping, allowing only vessels serving countries it deems friendly -- such as China -- to cross.
With his blockade of Iranian ports, the US president was trying to starve Iran of funds but also pressure Beijing, the biggest buyer of Iranian oil, to lean on Tehran to reopen Hormuz, according to analysts.
In a social media post, Trump said the bulk of Iran's navy had already been destroyed during the war, but that if any of what he said were Tehran's few remaining "fast attack ships" approach the blockade "they will be immediately ELIMINATED."
Qatari Foreign Minister and Premier Sheikh Mohammed bin Abdulrahman Al Thani urged both sides to guarantee freedom of navigation and refrain from using maritime routes "as a tool for pressure," encouraging Tehran and Washington to remain in touch with mediators.
Beijing criticized the blockade, with foreign ministry spokesman Guo Jiakun emphasizing the strait's importance to trade and saying that "maintaining its security, stability, and unimpeded flow is in the common interest of the international community."
UN chief Antonio Guterres also called for freedom of navigation to be respected and pointed to the 20,000 mariners trapped in the Gulf.
US Central Command said the blockade included "vessels of all nations entering or departing Iranian ports and coastal areas, including all Iranian ports on the Arabian Gulf and Gulf of Oman."
US forces would not impede vessels transiting the strait to and from non-Iranian ports, it added.
Iran's military command issued a statement branding the blockade an act of piracy, and warned that if the security of its harbors "is threatened, no port in the Persian Gulf and the Arabian Sea will be safe".
French President Emmanuel Macron said that France and Britain would host a conference with countries prepared to join a "peaceful multinational mission" to secure the strait, but it would be "strictly defensive" and only operational once circumstances permit.
