The US Senate has called for Sudan to allow humanitarian aid workers into restive Blue Nile and South Kordofan states where a quarter million people face food shortages, a US lawmaker said Friday.

A resolution promoting peace and stability in Sudan was agreed to by voice vote late Thursday, calling for "the government of Sudan to allow immediate and unrestricted humanitarian access to South Kordofan, Blue Nile and all other conflict-affected areas of Sudan."

It also urged an immediate cessation of hostilities in the border region, contested by South Sudan, to allow food and essential supplies to reach affected civilians.

Sudanese President Omar al-Bashir "has the ability to avert a further escalation of the humanitarian crisis, and has a responsibility to do so," the resolution's main sponsor, Democratic Senator Chris Coons, said in a statement.

The Senate joined international requests for Khartoum "to allow desperately needed humanitarian assistance to reach the more than 250,000 people in the region facing emergency food shortages," added Coons, who chairs the Senate Foreign Relations Subcommittee on Africa.

"The people of Southern Kordofan and Blue Nile have suffered for too long, and they can no longer wait."

Sudan has blockaded aid from entering the war zones, where government soldiers have been battling rebel fighters once allied to what became South Sudan last July.

Over 105,000 refugees have fled southwards from the boiling civil war in Blue Nile and Southern Kordofan, where civilians say they faced relentless bombing raids.

The UN refugee agency this week warned that the lives of thousands of Sudanese refugees were at risk as Khartoum bombarded South Sudan's oil-rich border areas.