The Biden administration is concerned that a weakened Iran could build a nuclear weapon, White House National Security Adviser Jake Sullivan said on Sunday, adding that he was briefing President-elect Donald Trump's team on the risk, Reuters reported.

Iran has suffered setbacks to its regional influence after Israel's assaults on its allies, Palestinian Hamas and Lebanon's Hezbollah, followed by the fall of Iran-aligned Syrian President Bashar al-Assad.

Israeli strikes on Iranian facilities, including missile factories and air defenses, have reduced Tehran's conventional military capabilities, Sullivan told CNN.

"It's no wonder there are voices (in Iran) saying, 'Hey, maybe we need to go for a nuclear weapon right now ... Maybe we have to revisit our nuclear doctrine'," Sullivan said.

Iran says its nuclear program is peaceful, but it has expanded uranium enrichment since Trump, in his 2017-2021 presidential term, pulled out of a deal between Tehran and world powers that put restrictions on Iran's nuclear activity in exchange for sanctions relief, read the report.

Sullivan said that there was a risk that Iran might abandon its promise not to build nuclear weapons.

"It's a risk we are trying to be vigilant about now. It's a risk that I'm personally briefing the incoming team on," Sullivan said, adding that he had also consulted with U.S. ally Israel.

Trump, who takes office on Jan. 20, could return to his hardline Iran policy by stepping up sanctions on Iran's oil industry.

Sullivan said Trump would have an opportunity to pursue diplomacy with Tehran, given Iran's "weakened state."

"Maybe he can come around this time, with the situation Iran finds itself in, and actually deliver a nuclear deal that curbs Iran's nuclear ambitions for the long term," he said.

Pakistan's Foreign Ministry on Saturday dismissed as unfounded and "devoid of rationality" assertions by a senior U.S. official that its missile programme could eventually pose a threat to the United States, Reuters reported.

Earlier this week, U.S. Deputy National Security Adviser Jon Finer said Pakistan's development of long-range ballistic missiles made it an "emerging threat".

Finer's comments, which came a day after Washington announced a new round of sanctions related to the ballistic missile programme, underscored the deterioration in once-close ties between Washington and Islamabad since the 2021 U.S. troop withdrawal from Afghanistan.

Addressing Finer's remarks, Pakistan's Foreign Ministry said the perception of an alleged threat was "unfortunate".

"These allegations are unfounded, devoid of rationality and sense of history," the ministry added in a statement.

The ministry said its strategic capabilities were solely for defending its sovereignty and maintaining regional stability, and should not be perceived as a threat to any other country.

It also highlighted Pakistan's long history of cooperation with the U.S., particularly in counter-terrorism efforts, and reiterated its commitment to engaging constructively on all issues, including regional security and stability, read the report.

Relations between the United States and Pakistan have seen significant ups and downs. The countries collaborated during the Cold War and in the fight against al Qaeda after 9/11.

However, ties have been strained due to coups in the South Asian country by Pakistan's military, support for the Taliban's 1996-2001 rule in Afghanistan, and over the nuclear weapons programme.