WASHINGTON (Reuters) - The U.S. envoy to Sudan and South Sudan urged the international community on Wednesday to be clear-eyed in dealing with armed Sudanese opposition groups which put political ambitions above the interests of their own people.

Donald Booth, speaking a day before he leaves office at the end of the Obama administration, said he recently talked with Sudan’s armed rebel group, the Sudan People’s Liberation Movement-North (SPLM-N) about a U.S. proposal to deliver food and medicine to conflict areas it controls but the group rejected the offer.

The comments came a week after the Obama administration moved to lift a 20-year-old trade embargo and ease financial sanctions against Khartoum, saying the government had cooperated in fighting Islamic State and other militant groups.

“I have found that some of the leaders of the Sudanese opposition, especially those with guns, are more than willing to ignore the interests and well-being of ordinary civilians, in favor of their long political ambitions,” Booth told a Washington forum.

“We need to be careful not to hold them in unquestioned high esteem. It is important to be clear-eyed about whom we are dealing with,” Booth said, referring to foreign governments and groups that back the opposition.

Booth said the SPLM-N’s rejection of the U.S. offer of humanitarian assistance at a meeting in Paris was a “huge missed opportunity to advance peace negotiations and help the people they claim to be helping.”

“Even though we hold the government to its commitments to peace, we must also demand that the opposition set aside personal political ambitions and put their people first,” he said.

The SPLM-N was previously part of the South Sudanese rebel group and is fighting in the border states of South Kordofan and Blue Nile.

“Just as there are hardliners within the Sudanese government who hold on to false notions that military victory can be achieved, so too there are leaders of the armed groups who believe they are right to fight on no matter what the cost to their people,” Booth said.

He launched talks in early 2015 with Sudanese President Omar al-Bashir’s then senior advisor, Ibrahim Ghandour, to try to improve ties between Washington and Khartoum after years of contentious relations.

The final decision on lifting U.S. sanctions on Sudan will go to President-elect Donald Trump after Khartoum takes more steps to end internal conflicts, allow more aid to conflict-torn areas, and help fight Islamic State and other groups.