US President Joe Biden's national security adviser Jake Sullivan is traveling to Saudi Arabia on Monday to hold discussions with Crown Prince Mohammed bin Salman about the situation in Yemen, the Associated Press reported.

At least 50 dead as fighting intensifies for Yemen's Marib

Sullivan is also expected to meet deputy defence minister Khalid bin Salman, a brother to the crown prince, according to the report, which cited sources.

Biden has taken a tougher stance with Saudi Arabia than his predecessor Donald Trump, criticising the kingdom over its human rights record while releasing a US intelligence report earlier this year implicating the Saudi crown prince in the 2018 killing of Saudi dissident journalist Jamal Khashoggi.

Saudi official in US for talks on Yemen, Iran, Khashoggi

The prince denies any involvement.

Earlier this month, the FBI released a newly declassified document about its investigation of the Sept. 11, 2001, attacks on the United States and allegations of Saudi government support for the hijackers, following an executive order by Biden.

The Kingdom has long said it had no role in the attacks.