The Biden administration is weighing unfreezing $1 billion in Iranian funds that the country could use for humanitarian relief, CNN reported on Thursday.

It is not clear whether the release of the funds would occur unilaterally, but one line of thought is that it could serve as a useful goodwill gesture to Tehran, said three people briefed on the internal deliberations.

The report comes amid negotiations for the US to reenter the 2015 nuclear deal and bring Iran back into compliance with its terms.

The funds would not be provided in cash; instead, they’d be allocated to a Swiss channel, known as the Swiss Humanitarian Trade Arrangement, which was set up last year to allow humanitarian aid like food and medicine to be sent to Iran without violating US sanctions, according to CNN.

The plan is facing opposition from Iran hawks in Congress who are privy to the discussions, said one Republican congressional staffer. The staffer said that some on Capitol Hill view the idea of unfreezing any of Iran’s money as a concession that would diminish the US’ leverage.

Iran has gradually scaled back its compliance with the 2015 deal in response to former US President Donald Trump’s withdrawal from the agreement in May of 2018.

It has continued to do so even as current US President Joe Biden has indicated a desire to return to the deal.

The talks in Vienna have involved diplomats from Britain, China, France, Germany, Iran and Russia who met the Iranian representatives, while US diplomats participated indirectly in the talks from a nearby hotel.

The US and European Union both said recently that more work was needed to revive the 2015 deal, while Iranian President Hassan Rouhani said the “negotiations have achieved 60-70 percent progress.”

A senior State Department official, speaking to reporters before a new round of talks begins in Vienna on Friday, said the negotiations so far had “helped crystallize the choices” that need to be made by both Iran and the US.