The United States won new assurances Tuesday that an important air base used to support the war in Afghanistan will remain open as long as necessary.

Rice and Kyrgyz President Kurmanbek Bakiyev (search) signed a brief statement promising open-ended U.S. use of the Manas air base for Afghan operations and a U.S. inquiry into whether past payments for use of the facility might have fallen into corrupt hands.

Rice is in Central Asia to celebrate democratic power in the region. Bakiyev earned the presidency earlier this year after the ouster of an increasingly authoritarian predecessor. He is also the prime minister of the nation.

Rice also wanted to firm up U.S. rights to the base, for which it pays about $40 million to $50 million a year.

"The duration of the (U.S.-led military) presence directly depends on the situation in Afghanistan," Bakiyev said after meeting with Rice.

Bakiyev has made similar promises on the base before, but has also wavered on the terms. The base has become particularly important since the government of neighboring Uzbekistan said the United States must leave a base there.

Both facilities, plus one in Afghanistan itself, are used heavily in the four-year-old war in Afghanistan. The Kyrgyz base Rice toured is also hosting some relief and supply efforts for Pakistan, where a weekend earthquake killed thousands. Rice may change her itinerary to visit Pakistan this week.

Tensions over military bases rose over the summer when the Shanghai Cooperation Organization (search), dominated by Russia and China, urged the U.S. military to withdraw its bases from both Uzbekistan and Kyrgyzstan. The move was seen as a joint effort by Russia and China to drive the United States out of the strategically placed, resource-rich region, and Bakiyev initially seemed to go along.

Kyrgyzstan also hosts a Russian base, and the country is still heavily influenced in language, architecture and culture by its years as a Soviet republic.

U.S. officials said Tuesday's agreement is the first time Bakiyev has put the base rights in writing, and represented his most explicit repudiation of the Russian and Chinese position.

Earlier Tuesday, Rice told several hundred U.S. troops at Manas that they are helping safeguard young democracies on former Soviet turf.

"Kyrgyzstan itself has just been through an extraordinary revolution. An extraordinary new day is before the Kyrgyz people if they can deliver on the democratic promise," Rice told some of the approximately 1,000 U.S., French and Spanish troops stationed there.

En route to the region Monday, Rice told reporters that the United States can live without the Uzbek base and is not seeking additional real estate in the region. U.S. officials say military installations in and around Afghanistan will handle the additional load.

U.S. troops will be in Afghanistan for a long time to come, and the difficulty of their mission was underscored Tuesday when suspected Taliban rebels ambushed a police convoy in southern Afghanistan and killed 19 officers.

It was the deadliest attack ever on the Afghan police force, which was set up soon after U.S.-led forces ousted the Taliban from power in 2001.

The attack comes amid a major resurgence in violence by Taliban-led rebels that has left about 1,400 people dead in the past half year. On Monday, two suicide bombers killed three people in the main southern Afghan city of Kandahar, a former Taliban stronghold.

U.S. officials say there is no Cold War-style power struggle in Central Asia, only a conflict between old ideas and new ones about political liberty and economic development.

"I will be talking about the importance of shared values," Rice said at the air base. "America has always been at its best ... when we stood for principle, not just for power."