The United States said on Wednesday it was discussing a possible second round of peace talks with Iran in Pakistan and was optimistic about reaching a deal, as Tehran threatened to shut down Red Sea trade unless Washington lifted a naval blockade on its ports.

A Pakistani delegation arrived in Tehran earlier Wednesday bearing a new message from Washington after President Donald Trump indicated talks could resume this week following last weekend's abortive negotiations in Islamabad.

White House Press Secretary Karoline Leavitt told reporters further talks "would very likely" be in the Pakistani capital, saying: "Those discussions are being had" and "we feel good about the prospects of a deal."

US Vice President JD Vance, who led the first round of talks, said Iran was being offered a "grand bargain" to end the six-week war and address the decades-old dispute over Tehran's nuclear programme.

Israeli Prime Minister Benjamin Netanyahu, meanwhile, said on Wednesday that Israel and the US had "identical" goals in Iran.

"We want to see enriched material removed from Iran; we want to see the elimination of enrichment capability within Iran; and, of course, we want to see the (Hormuz) strait reopened," he added.

Stocks rose and crude dropped as markets eyed chances of a deal to get oil flowing again through the strait -- choked by Iranian forces since the US-Israeli offensive began, and now the focus of the US blockade.

'Close to being over'
Washington has sought to turn the screws on Tehran with a blockade of its ports, with US Central Command claiming to have "completely halted economic trade going into and out of Iran by sea".

The picture based on recent maritime tracking data in the Strait of Hormuz was less clear-cut, and Iran's Tasnim news agency reported shipping has continued from southern Iran.

But the head of Iran's military central command centre warned a US failure to lift the blockade would constitute "a prelude" to violating the two-week ceasefire struck on April 8.

Unless Washington relents, Iran's armed forces "will not allow any exports or imports to continue in the Persian Gulf, the Sea of Oman and the Red Sea," said Ali Abdollahi.

Speaking to the New York Post on Tuesday, Trump said a new round of talks could take place in Pakistan "over the next two days", while telling Fox Business the war was "very close to being over".

On the Iranian side, a foreign ministry spokesman said "several messages" had been exchanged via Islamabad since talks wrapped up on Sunday.

Foreign Minister Abbas Araghchi on Wednesday welcomed a Pakistani delegation led by army chief Asim Munir in Tehran that Iranian state television said was to relay a new US message and discuss a second round of talks.

'Grand bargain'
Trump has insisted that any deal must permanently bar Iran from acquiring a nuclear weapon. He launched the war on February 28, arguing that Tehran was rushing to complete an atomic bomb, an assertion not backed by the UN nuclear watchdog.

Reports said Washington had sought a 20-year suspension of Iran's uranium enrichment programme during the Islamabad talks, and that Iran, in turn, proposed suspending its nuclear activity for five years -- an offer US officials rejected.

Tehran has always insisted its nuclear programme is for civilian purposes and its foreign ministry said Wednesday that Iran's right to enrich uranium was "indisputable", although the level of enrichment was "negotiable".

The US vice president said Tuesday that Trump had pledged to "make Iran thrive" if it committed to "not having a nuclear weapon".

"That's the kind of Trumpian grand bargain that the president has put on the table," Vance said, adding: "We're going to keep on negotiating and try to make it happen."

Lebanon talks
The latest signals on US-Iran talks came as Israel and Lebanon also agreed to open direct negotiations after their first high-level face-to-face meeting since 1993 took place Tuesday in Washington.

Netanyahu on Wednesday spoke of two central objectives in the negotiations with Lebanon: "First, the dismantling of Hezbollah; second, a sustainable peace... achieved through strength."

Trump's administration is pressing hard for an end to the conflict between Israel and Iran-backed Hezbollah militants in Lebanon, fearing it could jeopardise a broader settlement.

The US State Department said "all sides agreed to launch direct negotiations at a mutually agreed time and venue".

But the diplomatic push remained fragile with Hezbollah, which is hostile to any talks, firing dozens of rockets at Israel, whose military claimed hits on more than 200 targets linked to the militant group in Lebanon over 24 hours.

Israel's military chief of staff said he had ordered areas south of Lebanon's Litani River to be turned into a Hezbollah "kill zone" as troops pressed a major offensive there.

Lebanese authorities said Israeli strikes on the country's south killed at least three paramedics on Wednesday.