KHARTOUM, Feb 18 (Reuters) - Sudan's government on Saturday rejected U.S. accusations that genocide was ongoing in its Darfur region and said it was discussing allowing a robust U.N. force to take over from African peace monitors there.

U.S. Secretary of State Condoleezza Rice on Thursday said genocide was continuing in Darfur through a widespread campaign of rape, looting and killing and urged the African Union to accept the help of U.N. peacekeepers to stop the atrocities.

Underfinanced African Union troops form the only bulwark in Sudan against marauding militia and rebels.

"She (Rice) is biased because any authentic parties who are concerned with what's going on in Darfur have confirmed that this is not genocide," said Sudanese Foreign Ministry spokesman Jamal Ibrahim.

"This is a systematic policy of the U.S. administration ... of pressuring the Khartoum government," Ibrahim said, saying the United States was responding to internal pressures from Congress and the African American lobby.

Tens of thousands have been killed in Darfur since mostly non-Arab rebels took up arms in early 2003, accusing the central government of neglect. Khartoum has repeatedly denied U.S. charges of genocide.

Foreign Minister Lam Akol said he had not heard Rice's comments, but, he told Reuters: "of course there is no genocide in Darfur."

U.S. President George W. Bush said on Friday that double the number of peacekeepers than the already 7,000-strong African Union monitors and troops deployed there were needed to stop the violence in Darfur.

He said a NATO organisational role would be needed. U.N. chief Kofi Annan describes the transition of the AU force to the United Nations as "inevitable".

U.N. ROLE

Sudan has in the past refused to accept any troops other than African soldiers in Darfur.

But Khartoum has shown signs of softening its position. Ibrahim said on Saturday the government had not yet decided to accept or reject a change to a U.N. or other force.

"(But) it is not acceptable for any party to make a unilateral assessment of the role of the AU forces in Darfur," he added.

The United Nations has already begun contingency planning for such a move, which could take nine months to a year to complete. Additional money has been requested in the meantime for the AU force, which relies on donor nations.

The U.N. is deploying more than 10,000 peacekeepers to Sudan's south where a separate and bloodier civil war -- Africa's longest -- ended with a peace deal last year.

The AU has been accused of standing by and watching when civilians have been attacked, and have themselves become a target of ambushes and kidnappings in the vast region.

They have had limited success in halting attacks on the more than 2 million Darfuri refugees living in camps.

But the African body, which built its force up to its present strength from a mere 300 at the start of its deployment some 18 months ago, says it has suffered from unreliable funding and a lack of equipment.

An AU soldier shot and wounded his officer this month in a dispute over the late payment of salaries.

And fighting continues. On Saturday a Sudanese armed forces spokesman said an unidentified armed force attacked an army garrison in the town of Congo Harasa near the Sudan/Chad border.

"The attack was yesterday and the armed forces repulsed it inflicting ... dozens of losses on them," said the army spokesman. He said the attack, which lasted more than an hour, came from within Chadian territory and the force retreated there, but gave no further details of casualties.

The long porous Chad-Sudan border has few official crossings. Both countries accuse the other of supporting rebels in each other's territories, adding to the already tense situation in Darfur.