WASHINGTON, May 27: Republican presidential candidate Senator John McCain on Tuesday vowed to halt and reverse the proliferation of nuclear weapons and to promote democracy in countries like Pakistan if elected.

In a foreign policy speech to the Los Angeles World Affairs Council and later in an address to a campaign rally in Denver, Colorado, Mr McCain also warned that an immediate US withdrawal from Iraq would encourage Al Qaeda in places like Pakistan and Afghanistan.

“We share an obligation with the world’s other great powers to halt and reverse the proliferation of nuclear weapons,” he declared. “We should work to reduce nuclear arsenals all around the world, starting with our own.”

Mr McCain pledged to renew the nuclear non-proliferation treaty, saying that “the United States should lead a global effort at nuclear disarmament consistent with our vital interests and the cause of peace.”

A bitter, and often negative, rivalry between Democratic presidential hopefuls Barack Obama and Hillary Clinton has apparently increased Mr McCain’s chances of winning the November election.

His policies, if implemented, could increase pressure on the world’s two self-declared nuclear powers – India and Pakistan – and may also have a negative impact on a nuclear deal India is negotiating with the US.

Mr McCain, however, reserved most of his ire for Iran, saying that the US and other world powers must “prevent Iran -- a nation whose President has repeatedly expressed a desire to wipe off Israel from the face of the earth -- from obtaining a nuclear weapon.”

Mr McCain blamed previous US administrations for promoting autocracies in the Muslim world and vowed to end this practice.

“For decades in the greater Middle East, we had a strategy of relying on autocrats to provide order and stability,” he said. “We relied on the Shah of Iran, the autocratic rulers of Egypt, the generals of Pakistan, the Saudi royal family, and even, for a time, on military dictator Saddam Hussein.”

The US, he said, can no longer delude itself that relying on these ‘out-dated autocracies’ is the safest bet. “They no longer provide lasting stability, only the illusion of it,” he added.

Mr McCain, however, warned that the US must not act rashly or demand change overnight. “But neither can we pretend the status quo is sustainable, stable, or in our interests. Change is occurring whether we want it or not.

“The only question for us is whether we shape this change in ways that benefit humanity or let our enemies seize it for their hateful purposes.”

Mr McCain called for a new arms agreement with Russia that finds ways to reduce the number of nuclear missiles, and suggested that the US and Russia should jointly cut non-nuclear weapons as well.