A new round of in-person talks between the United States and Iran could be held as early as this week, two people familiar with the ongoing negotiations told NBC News.

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It comes after talks led by Vice President JD Vance in Pakistan over the weekend failed to reach a peace agreement to end the war. Both Vance and President Donald Trump offered hope for future talks on Monday, even as U.S. forces launched a blockade barring ships from entering or exiting Iranian ports.

Opening the Strait of Hormuz for a free flow of shipping is a major sticking point in the negotiations for any agreement, one of the people said. Iran’s nuclear capability is another, the second person said.

The U.S. asked Iran during the marathon talks in Islamabad that failed over the weekend for a 20-year suspension of uranium enrichment, the second person said. The Iranians agreed to three to five years, which Trump has said is not acceptable, the second person said.

The U.S. has also asked Iran to remove highly enriched uranium from the country, but Iran agreed to a “monitored process of down blending” — which is a process by which more dangerous, highly-enriched uranium is mixed with natural or less potent uranium to create a less potent material, according to the second person familiar with the ongoing negotiations.

A U.S. official told NBC News that there is continued engagement between the U.S. and Iran and forward motion on trying to get to an agreement.

Vance, speaking in an interview with Fox News on Monday, said there had been some “good conversations” with Tehran during the talks in the Pakistani capital.

Asked whether there might be more negotiations on the horizon, he said the question would be “best put to the Iranians, because the ball really is in their court.”

He added that there was a “grand deal to be had,” but it was up to Tehran to “take the next step.”

Trump said that the U.S. had been called “by the right people, the appropriate people, and they want to work a deal.” He said a day earlier that he didn’t “care” whether Iran returned to the negotiating table.

Vance said that the key sticking point in the talks centered around Iran’s enrichment of uranium.

“We must have the enriched material out of Iran,” he said, adding: “We must have their conclusive commitment to not develop a nuclear weapon.”

Vance said Tehran had shown some flexibility in talks over the weekend, but “didn’t move far enough.”

With the possibility of fresh talks on the horizon, Vance said, “if the Iranians are willing to meet us there, then this can be a very, very good deal for both countries. If they’re not willing to meet us there, that’s up to them.”

The International Atomic Energy Agency, the United Nations’ nuclear watchdog, has estimated that Iran has nearly 1,000 pounds of highly enriched uranium, enough for eleven nuclear weapons.

Tehran has maintained that its highly enriched uranium is still buried underground after U.S. airstrikes targeting enrichment facilities last year. It insists its nuclear program is peaceful and that it has no intention of seeking a nuclear weapon.

Iran’s armed forces accused the U.S. of “piracy” with the blockade and threatened ports across the Gulf if its own were hit.

But despite the risks of an intensifying standoff over Hormuz, the 2-week ceasefire in the conflict seemed to be holding.

Israel and Lebanon, meanwhile, were holding rare direct talks in Washington on Tuesday in an effort to defuse another flashpoint that threatened the deal.