In a show of support for the rebel forces struggling to oust Libya's embattled dictator Moammar Gadhafi, U.S. Senator John McCain is touring their de facto capital of Benghazi on Friday.

Although details of his visit are shrouded in secrecy, McCain planned to meet with the rebel National Transition Council that now effectively controls the eastern half of the country, as well as members of the rebel armed forces.

As the most senior Republican on the U.S. Senate Armed Services Committee, McCain was among America's first and most outspoken proponents of U.S. military intervention in the restive North African nation.

When the U.S. stopped its air strike operations and handed control of the military effort to NATO, McCain warned that the move amounted to abandoning a fight for freedom.

At a news conference in Benghazi on Friday, he made it clear his position has not changed.

"Now we need to increase our support so that the Libyan people can achieve the only satisfactory outcome to this mass protest for universal rights: The end of Gadhafi's rule and the beginning of a peaceful and conclusive transition to democracy that will benefit all Libyans," the Arizona Republican said.

"I fear a stalemate could lead to the emergence of radical Islamic extremists."

McCain also described meeting young people during his morning tours of the city who had been transported from Misrata to Benghazi for treatment of injuries suffered in clashes with pro-Gadhafi forces.

"They're dying," he said. "They're brave young people who have sacrificed themselves and their lives for their country. It seems to me that the call should go out to help these people enjoy freedom and peace."

McCain's visit comes the day after the United States pledged rebel forces round-the-clock use of a pair of armed flying drones aimed at breaking what has developed into a deadlock between pro-Gadhafi forces and the rebels desperately trying to maintain control of their only foothold in western Libya, Misrata.

Because NATO airstrikes there have been stymied by the close proximity of Gadhafi's forces to the civilian population, it is hoped the unmanned Predator aircraft -- with their ability to fly lower and closer to urban targets than fighter jets -- might be able to more precisely target their strikes.

Although the first Predator mission in Libya was launched Thursday, U.S. Marine Gen. James Cartwright said the aircraft returned without firing its Hellfire missiles due to poor weather conditions.

In other developments Friday:

A fourth ship chartered by the International Organization for Migration is leaving Benghazi for Misrata, laden with 160 tons of food, medical supplies, tents and mattresses. So far IOM-chartered vessels have ferried more than 3,100 from the war-torn western city to the rebel-controlled east.

Refuting Libyan government claims of a day earlier, rebel forces said they are in control of the Dhuheiba crossing at the Tunisian border.

Rebels raised flags atop several buildings in the central part of Misrata, reasserting control of the strategic area a day after they drove pro-Gadhafi snipers away.

With files from The Associated Press