The two Democrats last month agreed to lift objections to a $1.2 billion arms sale to the UAE by the then administration of fellow Democrat Joe Biden after the White House said the Gulf power assured it was "not now transferring any weapons" to the paramilitary group.

But the lawmakers, Senator Chris Van Hollen and Representative Sara Jacobs, said briefings with Biden administration officials before they left office last weekend indicated that the UAE had broken its promises.

"Based on my conversations with the Biden administration, it's clear that the UAE is continuing to provide weapons to the murderous RSF, violating the assurances provided to the former administration," Van Hollen said in a statement.

"It is imperative that the United States not provide weapons to countries that are in turn providing military support to the RSF and complicit in its genocidal actions," he said.

Both vowed to attempt to block any arms sales under President Donald Trump, who in his last term negotiated a major package for the UAE.

"I will try to block any future offensive arms sale to the UAE in a push for peace, aid, justice and accountability for the people of Sudan," Jacobs said.

In the final days of the Biden administration, then secretary of state Antony Blinken said the RSF had committed genocide in Darfur, the scene of a scorched-earth campaign by the paramilitary unit's predecessor two decades ago.

The State Department accused the RSF, which is predominantly Arab, of systematic abuses targeting Darfur's non-Arab population including the killing of men and boys and sexual assault of women and girls.

The UAE has repeatedly denied arming the RSF despite international criticism and a finding by United Nations experts that the allegations were credible.

The paramilitary fighters forged a relationship with the UAE fighting Yemen's Iranian-backed Huthi insurgents.

Other powers including Egypt, Turkey, Iran and Russia have also been accused of supporting sides in the war between dueling generals, which has claimed tens of thousands of lives and triggered a humanitarian crisis.

Blinken on leaving office said neither general was fit to lead Sudan as he imposed sanctions on both.

But US officials say both sides feel they can still triumph on the battlefield, with Sudan's army saying Friday it had broken a siege on its headquarters in place since the war began in April 2023.