WASHINGTON (Reuters) - Archbishop Desmond Tutu of South Africa on Wednesday urged the U.S. Senate to pass a bill that would more than triple spending to fight AIDS, malaria and tuberculosis in Africa and other parts of the world.

The U.S. House of Representatives passed the legislation in April, but it has stalled in the Senate amid opposition by Sen. Tom Coburn of Oklahoma and a handful of other Republicans.

The bill calls for $50 billion in U.S. funding for programs fighting AIDS, tuberculosis and malaria in Africa and other parts of the world over the next five years. The AIDS epidemic has hit sub-Saharan Africa the hardest.

The measure marks a big hike from the $15 billion authorized over the first five years of the initiative.

AIDS activist groups have been calling on the Senate to pass the bill, which embodies one of President George W. Bush's foremost foreign aid initiatives, and send it to Bush to sign into law.

"You have already saved millions of lives. And the new legislation has the potential for sustaining a response, to build on all of the gains that have already been achieved," Tutu, the Nobel Peace Prize laureate, told reporters in a conference call arranged by the group Global AIDS Alliance.

"I plead to the leaders, the members of Congress -- please, please for the sake of the world, for the sake of the future, expedite the passing of the relevant legislation," Tutu added.

Tutu this month wrote letters to Senate leaders saying he was troubled by the impasse over the bill, and asking them to redouble efforts to bring it to the Senate floor for a vote.

Bush initially proposed doubling the program to $30 billion, but the Democratic-led House boosted it to $50 billion. Coburn and the other senators opposing it have called for more of the money to go to treat people already infected with HIV rather than prevention efforts and other purposes.