MOSCOW — President Barack Obama and Russian President Dmitry Medvedev struck a preliminary deal Monday to reduce their nations' stockpiles of nuclear warheads to as few as 1,500 each, pointing their arsenals toward the lowest levels of any U.S.-Russia arms control agreement.

The document signed by the two leaders at a Moscow summit, Obama's first in Russia, is meant as a guide for negotiators as the nations work toward a replacement pact for the START arms control agreement that expires in December. The joint understanding completed by Obama and Medvedev, signed after about three hours of talks at the Kremlin, also commits the new treaty to lower longer-range missiles for delivering nuclear bombs to between 500 and 1,100.

Under current treaties, each country is allowed a maximum of 2,200 warheads and 1,600 launch vehicles.

A White House statement said the new treaty "will include effective verification measures."

"The new agreement will enhance the security of both the U.S. and Russia, as well as provide predictability and stability in strategic offensive forces," the statement said. The two leaders were to appear together at a Kremlin news conference to discuss their agreement.

The leaders announced several other deals meant to show progress toward resetting badly damaged U.S.-Russian relations, including permission from Moscow for the United States to transport arms across its land and airspace into Afghanistan for the war there. The White House says the deal will save the U.S. $133 million a year, by waiving transit fees and shortening flying time.

They outlined other areas in which they said their countries would work together to help stabilize Afghanistan, including increasing assistance to the Afghan army and police, and training counternarcotics personnel. A joint statement said that they welcomed increased international support for upcoming Afghan elections and that they were prepared to help Afghanistan and Pakistan work together against the "common threats of terrorism, extremism and drug trafficking."

Other side agreements meant to sweeten Obama's two days of talks here include revival of a joint commission to try to account for missing service members of both countries dating back to World War II and fresh cooperation on public health issues. The commission was first created by the first President Bush and President Boris Yeltsin in the early 1990s, but the Russians later downgraded their participation. The U.S. hope is that the Russians will open some of their more sensitive archives to U.S. researchers seeking details about missing American servicemen.