Russian President Dmitry Medvedev said Sunday the United States must compromise on its plan to build a missile defense system in Europe in order to reach a deal on reducing nuclear warheads, Reuters reported.

The Russian leader said in an interview that a deal on the Strategic Arms Reduction Treaty (START I) and the United States' plan for a missile defense system are linked. Moscow believes a missile defense system is a threat to its national security.

"We consider these issues are interconnected," Medvedev said. "It is sufficient to show restraint and show an ability to compromise. And then we can agree on the basis of a new deal on START and at the same time can agree on the question of how we move forward on anti-missile defense."

President Obama is aiming to rebuild relations with Russia as part of his weeklong trip abroad this week, anchored around a yearly meeting of leaders from the world's industrial powers in Italy. He departs for Moscow Sunday night.

Obama set a tone for the Moscow meeting by saying in an Associated Press interview Thursday that he was off to a good start with Russian President Dmitry Medvedev. But, Obama added, Vladimir Putin -- Medvedev's predecessor and the current prime minister -- "still has a lot of sway in Russia."

Obama has separate meetings with them.

"I think Putin has one foot in the old ways of doing business and one foot in the new," Obama said in the interview. Putin responded Friday by poking fun at Obama's imagery and saying the new U.S. president is wrong about him. A Putin spokesman said Obama would change his mind after meeting Putin.

"Putin knows that, given Medvedev's position, he's the guy who deals with foreign leaders," said Stephen Sestanovich, a Russian expert at the Council on Foreign Relations. "But Putin wants to find ways of reminding everybody who's really in charge. And I don't doubt that he will find ways of doing that."

The rhetoric leading up to the summit reflects the complex relationship between the countries.

Putting down a friendly marker of his own before Obama shows up, Medvedev noted that conditions had worsened in recent years but now there is "only one road to follow -- the road of agreement."

Obama expects to emerge from Moscow with a framework for how the U.S. and Russia will go about reducing their stockpile of nuclear warheads. He and Medvedev stated their intentions toward that goal in April during a London meeting that had both leaders talking of a fresh start.

Any tangible progress now will be held up as proof of better U.S.-Russia ties, and a step toward broader cooperation on ridding the world of nuclear arms.

Yet there is harder work ahead to determine how many weapons both sides will give up and how those steps will be verified. Both sides hope to have a final deal in place before the Strategic Arms Reduction Treaty expires in December.

Obama plans to give a major address on U.S.-Russia relations and meet with a range of civic leaders, hoping to turn around Russian attitudes of the U.S.

The Associated Press contributed to this report.