BRUSSELS (Reuters) - The new head of NATO said he wanted Afghan forces to assume lead responsibility for security within the next four years, but would not set a timeline for a complete pull out by alliance troops.

Anders Fogh Rasmussen, who took over as secretary-general of the North Atlantic Treaty Organization on Saturday, faces many challenges but none more daunting than finding a winning strategy for the war in Afghanistan and improving relations with its former Cold War foe Russia.

Afghanistan remains a priority and will require a comprehensive approach involving both military and civilian efforts to stabilize the country ahead of elections this month, Rasmussen told Reuters in an interview.

July was the deadliest month for foreign forces in Afghanistan since the Taliban were ousted in 2001, with at least 71 killed. August has followed that trend with violence escalating ahead of the August 20 poll.

Rasmussen, 56, has to persuade reluctant European allies to commit more troops, money and other resources to Afghanistan. The recent rise in casualties, especially British, has led to greater public questioning of the reasons for NATO involvement.

“I believe that during my term as NATO secretary-general, Afghans must take over lead responsibility for security in most of their country,” Rasmussen later told a news conference in Brussels.

He refused to set a timeline for NATO troops’ withdrawal but said the ultimate goal was to hand responsibility for security to Afghan security forces gradually, province by province, during his term of office.

This does not mean a quick NATO exit, he added. “Let no Taliban propaganda say that what I say means a run for the exit -- it is not. We will support the Afghan people for as long as it takes,” Rasmussen said.

“It will not be easy and the past months have made that bitterly clear,” he added.

NEGOTIATE WITH MODERATES?

The independent Danish daily Politiken said the new NATO chief favored negotiating with moderate Taliban elements as a means of splitting the insurgents, a position that has also gained the support of British Foreign Secretary David Miliband.

“There is quite clearly a hard core that it’s impossible to reach any agreement with. They only have respect for military power. But there are also groups that you can talk with in an attempt to create some reconciliation in Afghan society,” the paper quoted Rasmussen saying in an interview on its website.

Rasmussen said his other goal, at the start of his NATO tenure, would be to pursue the drive for a strategic partnership with Russia, while urging Moscow to respect the sovereignty and integrity of its neighbors.

The former Danish prime minister also has the delicate task of managing expectations in Ukraine and Georgia, former Soviet republics that have been promised eventual NATO membership despite Moscow’s opposition.

Rasmussen said the 28-member alliance and Russia had common goals in counter-terrorism, Afghanistan, disarmament and non-proliferation.

“I think we should develop practical cooperation ... while of course insisting on Russian compliance with its international obligations including respecting the territorial integrity and political freedom of its neighbors,” Rasmussen said.

NATO’s relations with Russia were damaged by the five-day Russia-Georgia war last year. Rasmussen will try to repair this damage, mindful also of the need to cooperate with Russia on global security issues.

The alliance has put the subject of Georgian and Ukrainian NATO membership on the back burner in the interests of getting relations with Moscow back on track, but says membership remains open to countries that meet NATO standards.