Blinken, on visits to Egypt and Qatar mostly focused on bringing a ceasefire in the Gaza war, said he also consulted on the US-brokered talks on Sudan underway in Switzerland.

"With everything else going on in the world, the worst humanitarian situation in the world right now is in Sudan," Blinken told reporters as he left Doha.

"There are more people in Sudan who are suffering from fighting, from violence, from lack of access to food and basic humanitarian assistance," Blinken said.

The United States said Monday that the talks in Switzerland were finalising ways to open three humanitarian routes for badly needed food, including a critical crossing from Chad.

"We obviously need to see that move forward, but that's critical in bringing life-essential assistance to people who desperately need it," Blinken said.

"As we're doing that, of course, we're working on trying to get a broader agreement on a cessation of hostilities," he said.

The US point man on Sudan who is leading negotiations, Tom Perriello, joined Blinken for his talks earlier Tuesday with the Egyptian President Abdel-Fattah El-Sisi in the coastal city of El Alamein.

Perriello said he would also meet with a Sudanese government delegation in his latest bid to persuade Sudan's army to take part in the talks.

War broke out in April last year between The Sudanese Armed Forces (SAF) and the paramilitary Rapid Support Forces (RSF), devastating what was already one of the world's poorest nations.

More than 25 million people, over half of Sudan's population, face acute hunger, according to UN agencies, with famine declared in a displacement camp in Darfur, which borders Chad.

The RSF has sent a delegation to Switzerland but the army has refused to join.

Perriello has consulted with the army remotely and Blinken has twice called army chief Abdel Fattah al-Burhan to press him to participate.

* This story was edited by Ahram Online.