The president of Kazakhstan agreed Sunday to allow over-flights by U.S. planes carrying troops and equipment to Afghanistan, a step expected to help open a route that will move forces into the war zone more quickly and safely, officials said.

Michael McFaul, the senior director for Russia on the National Security Council, told reporters in a conference call that the agreement will allow troops to fly directly from the United States over the North Pole to the region. Previously, cargo went through Pakistan or was sent on a longer, more complicated east-west journey.

"This will save money; it will save time in terms of moving our troops and supplies needed into the theater," McFaul said.

The U.S. government has been seeking alternatives to its supply route through Pakistan's Khyber Pass, which the Taliban has often attacked. Last summer, Washington signed an agreement with Moscow that was expected to allow annually as many as 4,500 flights over its territory. But that accord has been slow to be realized, in part because of the lack of ability to fly over Kazakhstan, which sits between Russia and Kyrgyzstan, where the United States has a key transit base for Afghan flights, officials said.

The formal agreement will probably not be concluded for weeks, as details are worked out, officials said. But Sunday's meeting between Obama and Kazakh President Nursultan Nazarbayev was the turning point, they said.

Although U.S. officials had been seeking an accord for months with their Kazakh counterparts, "it's only the president that will make this happen," said a senior administration official, speaking on the condition of anonymity to discuss diplomatic issues.

The presidents were meeting a day before a nuclear security summit that has drawn dozens of heads of state to Washington.

Kazakhstan also signed an agreement with NATO in January allowing nonlethal cargo to travel by rail across its territory.

The Obama administration has been eager to line up better transit routes into Afghanistan as it increases troops in the country. But the future U.S. use of a key base in Kyrgyzstan was thrown into doubt last week when the opposition toppled the government there.