Updated

The leader of the brutal rebel group the Lord's Resistance Army has crossed back into Congo after having been in Sudan, a Ugandan official said Friday, while a U.S. official said he has seen no evidence Sudan was helping the rebel leader.

Joseph Kony entered the Darfur region of Sudan in October, according to the Ugandan military, and Ugandan officials were worried he may have been receiving support from officials in Sudan's capital.

Khartoum once backed Kony but severed the relationship in 2005, at the signing of a peace agreement between Sudan's north and south. Southern Sudan on Saturday wraps up a seven-day vote on an independence referendum likely to lead to the creation of the world's newest country.

Karl Wycoff, the U.S. Deputy Assistance Secretary for African Affairs said Friday he has seen no evidence of support from Sudan to the LRA, though he said he was aware of the allegation.

"It's something we closely monitor," Wycoff said during a telephone conference with journalists.

Ugandan army spokesman Felix Kulayigye said Kony has left Darfur and crossed back into Congo. Kulayigye, who did not say when Kony crossed back over, also said Ugandan officials have no evidence of any support to Kony from Khartoum.

Kony, like Sudan's president, is wanted by the International Criminal Court. Kony's group has been accused of mass kidnappings, killings and other atrocities since it began its attacks in Uganda more than 20 years ago. Kony's 2005 ICC warrant seeks him for crimes against humanity in his native Uganda.

In November the U.S. announced a new strategy to counter the LRA's attacks on civilians. U.S. legislation passed last year called for the coordination of U.S. diplomatic, economic, intelligence and military efforts against the LRA.

The U.S., Wycoff said, has been working for years to a resolution of the LRA problem, including support of regional military efforts.

"We applaud the efforts to eliminate the threat posed by the Lord's Resistance Army," Wycoff said.

U.S. Gen. William Ward, the commander of the U.S. military's Africa command, met with Ugandan military leaders last Sunday, during which they discussed the hunt for Kony, said Kulayigye.

In late 2008 the Ugandan government launched Operation Lighting Thunder, a hunt for Kony's group that forced LRA fighters to scatter in small groups. Pockets of fighters are believed to be operating in Sudan, Congo, and Central African Republic.

Uganda's military is the primary force searching out Kony and his men in all three of those countries. The Small Arms Survey, a research project that monitors armed violence, said Friday that Uganda has 2,400 troops in the three countries searching for LRA fighters. That is down from 7,000 troops two years earlier, the Small Arms Survey said.

Estimates of the LRA's overall strength are in the 200 to 400 range.

A report from the Enough Project last year said that Kony no longer has complete and direct command and control over each LRA unit because they scattered. The LRA is now at its weakest point in 15 years, and Kony has less influence over his troops than ever before, the report said.