Russia and the United States have a good chance at signing a new nuclear arms reduction deal before year's end, but other nuclear powers must join disarmament efforts, Russian President Dmitry Medvedev said in remarks released Saturday.

Medvedev also told Germany's Der Spiegel magazine that he has been working well with his predecessor Vladimir Putin, and that predictions of a rift between him and Putin, who is widely seen as pulling the strings in Russia, are overblown. The comments were released by the Kremlin.

"No one must have any doubts that our 'tandem' has been working quite harmoniously," Medvedev said. "As you can see, predictions that we will have a falling out so far have failed to materialize."

The U.S.-Russian arms control talks are moving at a good pace, Medvedev said. "We have every chance to agree on a new treaty, determine new (weapons) levels and control measures and sign a legally binding document in the end of the year," he said in remarks released by the Kremlin.

He sounded less upbeat about the prospect of the complete abolition of nuclear weapons. President Barack Obama and Medvedev both said last April they were committed to stopping the proliferation of nuclear arms.

Medvedev told Der Spiegel that other nuclear powers have been reluctant to join in disarmament efforts. "A nuclear-free world is our shared ideal for which we must aspire, but a road to that is difficult," he said. "It takes not just the United States and Russia renouncing nuclear weapons, but other countries as well."

Putin anointed Medvedev as his preferred successor and moved into the prime minister's job after the 2008 presidential election. Putin said in September that he and Medvedev would "come to an agreement" on who would run for president in the 2012 election, leading to speculation that the two would decide on a predetermined winner.

Medvedev maintained that Putin meant to say they would discuss who should run for president to "avoid elbowing each other."

"He did not say that we would decide between us who will be the next president," Medvedev said. "This would be ridiculous."

"I do not wish to one day find myself and Vladimir Putin resembling the aged leaders from the Soviet Communist Party Politburo standing on Lenin's Mausoleum in similar coats and hats."

Medvedev has championed the rule of law and civil rights, but critics said he has remained in Putin's shadow and failed to add substance to his pledges.

Medvedev and Putin sounded differently on some policy issues, but many observers saw it as a reflection of Medvedev's effort to raise his profile rather than real disagreements with his predecessor.

Medvedev told Der Spiegel that Russia could back sanctions against Iran if it fails to take a constructive stance in international talks over its nuclear program.

The statement echoed Medvedev's earlier comments, but Putin has warned that the threat of sanctions could thwart talks. Putin also has said, however, that there is no real difference between him and Medvedev on the subject.

Asked to comment on Putin famously calling the Soviet collapse "the greatest geopolitical catastrophe of the 20th century," Medvedev challenged his mentor.

He said that the Soviet breakup was a "serious, dramatic" event, but added that World War II and the 1917 Bolshevik revolution were real catastrophes.

Medvedev also set himself different from Putin by sharply criticizing the rule of Soviet dictator Josef Stalin.

"From the point of view of the law, killing of a huge number of compatriots for political or unsubstantiated economic motives is a crime," he told Der Spiegel in comments which followed a similar statement in a blog last week. "The rehabilitation of those involved in these crimes is impossible, no matter what economic achievements were made then and how well the state mechanism was built."

Putin has largely avoided talk about Communist crimes, and critics have accused him of whitewashing history and encouraging a more positive view of Stalin.