Iran has no plans to hold a second round of talks with the United States, Foreign Ministry spokesperson Esmail Baghaei said on Monday, deepening uncertainty over whether negotiations will proceed in Islamabad despite the expected arrival of US envoys.

Baghaei said it was "impossible" for Tehran to overlook the heavy costs of the past year and Washington's "repeated betrayals" of the diplomatic process. He accused the US of violating international law during negotiations on two occasions in recent months, including through attacks that harmed Iranian citizens and state assets, adding that all government bodies are maintaining heightened vigilance.

The White House said earlier that US Vice President JD Vance would lead a delegation to Islamabad for the second round of talks, while President Donald Trump said US officials would arrive in the Pakistani capital on Monday.

For his part, Baghaei said Iran will take its national interests and security as the top priority in deciding whether to continue the talks.

The remarks come amid escalating tensions around the Strait of Hormuz, through which roughly one-fifth of the world's oil supply passes, after US Marines seized an Iranian-flagged container ship on Sunday as part of Washington's naval blockade of Iranian ports. Trump has refused to lift the blockade despite Tehran's earlier declaration that the strategic waterway was fully open. Iran has since reclaimed control of the energy chokepoint.

It is not possible for Iran to unilaterally restore normal traffic in the Strait of Hormuz due to the "warlike situation" imposed by the US, including its ceasefire violations and threats against Iranian ports and vessels, Baghaei said.

The renewed tensions are threatening a fragile ceasefire set to expire on Wednesday, two weeks after it was brokered by Pakistan. It remains unclear whether the ceasefire will be extended, but Trump has threatened to "drop bombs again" if no deal is reached before the ceasefire's expiration.

Baghaei reiterated that Iran would not accept any deadlines or ultimatums, warning that any new "adventurism" by the US or Israel would be met with a "decisive response" from Iranian armed forces.

On Iran's nuclear program, Baghaei dismissed reports that Tehran might transfer its enriched uranium stockpile abroad, saying such an option "is not on the agenda" and that Iran remains committed to retaining its nuclear achievements within its territory.

Earlier reports suggested that Iran has floated suspending enrichment for up to five years and diluting its highly enriched uranium, while the US has pushed for a 20-year moratorium and full removal of the stockpile. 

The two countries are also discussing a proposal under which Washington would release $20 billion in frozen Iranian funds in exchange for Tehran relinquishing its current holdings, Axios reported.

Earlier on Monday, Ebrahim Azizi, a senior member of Iran's parliament, said Tehran remains open to negotiations with Washington, but not "at any cost" or under conditions imposed by the other side.