MOSCOW – Presidents Barack Obama and Dmitry Medvedev confidently committed to a year-end deal to slash nuclear stockpiles by about a third on Monday, but the U.S. leader failed to crack stubborn Kremlin objections to America's missile defense plans — a major stumbling block to such an agreement.

Both men renewed pledges to pull U.S.-Russian relations out of the dismal state into which they had descended during the eight years of the Bush administration. And to that end, they signed a series of agreements and joint statements designed to enliven and quicken contacts on a broad range of issues — including cooperation on Afghanistan, a key Obama foreign policy objective.

Obama said the leaders both felt relations had "suffered from a sense of drift. President Medvedev and I are committed to leaving behind the suspicion and rivalry of the past."

His host expressed similar good will.

"This is the first but very important step in improving full-scale cooperation between our two countries, which would go to the benefit of both states," the Russian leader said. But he injected a note of caution, saying discussions so far "cannot remove the burden of all the problems."

There was no statement of Russian readiness to help the United States persuade Iran to abandon its nuclear ambitions, even though Obama's top Russia adviser, Michael McFaul, told reporters in a post-meeting briefing that Iran dominated the two leaders' private meeting that opened the summit. Talks continued in an expanded session that included 12 advisers for each president.

For all the upbeat public statements, a pall of disagreement on missile defense and NATO expansion lingered over the glittering Kremlin hall where Obama and Medvedev answered reporters' questions. Obama said the meetings had been "frank," diplomatic speak for difficult.

Obama sits down on Tuesday with Medvedev's patron and predecessor as president, Prime Minister Vladimir Putin, the target of a verbal poke from the U.S. president last Friday. In a pre-summit interview with The Associated Press, Obama said Putin still had one foot in the old, Cold War way of doing things.

While Medvedev insisted on Monday that a replacement to the keystone START I nuclear arms reduction treaty, which expires Dec. 5, must be linked to Russian concerns about the U.S. missile defense program in Eastern Europe, it remained unclear if the Kremlin was prepared to scuttle the negotiations over that issue.

Gary Samore, Obama's chief adviser on weapons of mass destruction and arms control, told reporters he did not believe the Russians were prepared to walk away.

"I think at the end of the day — because our missile defense does not actually pose a threat to Russia's strategic forces — I think they'll be prepared to go ahead without trying to extract a price on missile defense."

And McFaul said it had been made "crystal clear" from the beginning that negotiations about a START replacement would not include any missile defense issues.

Washington insists the defense program is designed only to protect European allies from missile attack by Iran.

Hoping to ease Kremlin concerns, Obama promised that an assessment of whether the missile defense would actually work would be finished by late summer, earlier than expected, and that he would share initial U.S. thoughts with Medvedev.

Obama also said he understood in principle that arms control must take into account both offensive and defensive weapons. But he insisted the missile defense installations planned for Poland and the Czech Republic would pose no threat to Russia. He said they were not being built to intercept missiles from "a mighty Russian arsenal."

Obama does not approach the missile defense issue with the same fervor as former President George W. Bush, whose administration was responsible for reaching agreement with the two former Soviet satellites to serve as sites for the system.

The planned START replacement pact — the centerpiece summit agreement — calls for each side to reduce strategic warheads to a range of 1,500 to 1,675, and strategic delivery vehicles to a range of 500 to 1,100. Current limits allow a maximum of 2,200 warheads and 1,600 launch vehicles. The new treaty, as conceived, would run for 10 years. Each side would have seven years to reach reduction goals with the final three years used for verification.

Medvedev called the plan a "reasonable compromise."

Among the deals meant to sweeten Obama's two days of talks here and show progress toward resetting U.S.-Russian ties was a joint statement on Afghanistan. It included a deal to allow the United States to transport arms and military personnel across Russian land and airspace into Afghanistan.

The White House said that would save $133 million a year, through a transit fee waiver, shorter flying times and fuel savings.

The presidents 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 they welcomed increased international support for upcoming Afghan elections and were prepared to help Afghanistan and Pakistan work together against the "common threats of terrorism, extremism and drug trafficking."

Among other side agreements was the resumption of military cooperation, suspended after Russia invaded neighboring Georgia last August and sent relations into a nosedive. Last August, after the Georgian president ordered his military to try to retake the breakaway region of South Ossetia, Russia invaded and crushed the tiny nation's military.

McFaul said Obama would never accept Russia's contention that South Ossetia and Abkhazia, another breakaway Georgia region, are no longer part of Georgia.

Putin has voiced deep anger with Georgia's coziness with the United States as it lobbies to join NATO, and the standoff about Georgia is likely to be a central issue when Putin meets with Obama on Tuesday.

Obama also will deliver a speech Tuesday to graduates of Moscow's New Economic School in a bid to reach out to the Russian people. In addition, he plans to meet with opposition leaders who are continually under government pressure for their complaints about retreating democracy and freedom under Putin.

___

Associated Press Writer Ben Feller contributed to this report.