WASHINGTON (Reuters) - President Barack Obama on Monday renewed U.S. sanctions against Sudan's government, keeping pressure on Khartoum to stick to the timetable for holding a referendum that could split the country in two.

But Washington also held out for the prospect for reconsidering its tough approach if Sudanese leaders make progress in resolving the country's bitter north-south dispute and improving the situation in the troubled Darfur region.

Sudan is 10 weeks away from the scheduled start of a referendum that could lead to independence for its oil-producing south. If mishandled, the referendum could destabilize the region.

The White House issued a letter from Obama to Congress saying he was extending long-standing economic sanctions, a notice required by law each year to keep them in place.

The measures restrict trade and investment in Sudan and also block the assets of the Sudanese government and certain officials, among other things.

With trust low as both sides in the referendum exchange recriminations, progress has slowed on resolving volatile disputes such as the status of the oil-producing Abyei region, determining citizenship and forging an oil-sharing accord.

White House spokesman Tommy Vietor said the United States hoped Sudan's leaders "will make the urgent and difficult choices necessary to secure peace for the Sudanese people."

"As we work to support these choices, the United States will review the Sudanese government's progress on resolving outstanding (peace agreement) implementation issues as well as other relevant circumstances, to include improving security and humanitarian access in Darfur," he said.

"If the government of Sudan acts to improve the situation on the ground and advance peace, we stand ready to work with Sudan to ensure its rightful place in the international community.

Obama last week stressed the need to go ahead with the vote as scheduled when he spoke to former South African President Thabo Mbeki, who has tried to overcome obstacles in the north-south peace process as head of an African Union panel.

(Reporting by Matt Spetalnick; editing by Todd Eastham)