Khartoum -- Washington has been stepping up diplomatic pressure as its regional partners attempt to push Sudan's warring commanders toward a humanitarian truce after two years of conflict.

US President Donald Trump's envoy for Africa, Massad Boulos, on Tuesday urged Sudan's rival commanders to accept an international ceasefire proposal "without preconditions" in a conflict that has devastated the country for more than two years.

His appeal comes as diplomatic efforts intensify after Trump said last week he would personally engage in efforts to end the war.The latest truce proposal, presented on behalf of the US, the United Arab Emirates, Saudi Arabia and Egypt, has not been released publicly.

However, Sudanese army chief Abdel Fattah Burhan called it "unacceptable," while his rival and former deputy, Rapid Support Forces (RSF) leader Mohamed Hamdane Daglo, announced a unilateral three-month humanitarian ceasefire on Monday.

However, on Tuesday the army said it had fended off an attack on a base in Babanusa in West Kordofan state, the war's newest frontline.

"We are calling on both parties to accept the humanitarian truce as presented without preconditions," Boulos said in Abu Dhabi, adding that neither side had approved the text. "We would like them to accept the specific text that was presented to them."

Boulos spoke alongside Emirati presidential adviser Anwar Gargash, days after Burhan accused the mediation of bias because the UAE — widely accused of supporting the RSF — is part of the process. Abu Dhabi denies supplying weapons, fighters or fuel to the RSF despite evidence cited in international reports and independent investigations.