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

Medvedev also told Germany’s Der Spiegel magazine he has been working well with his predecessor, Vladimir Putin, and predictions of a rift between him and Putin are overblown. The Kremlin released a transcript of the comments.

“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.

Russia and the United States both say they are committed to negotiating a successor deal to their 1991 Strategic Arms Reduction Treaty. That arms reduction treaty has gradually slashed both sides’ arsenals but is set to expire Dec. 5.

He sounded less upbeat about the prospect of the complete abolition of nuclear weapons.

“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 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 say he has remained in Putin’s shadow and failed to add substance to his pledges.

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. But Putin also has said there is no real difference between him and Medvedev on the subject.

Asked to comment on Putin’s remark that the Soviet collapse represented “the greatest geopolitical catastrophe of the 20th century,” Medvedev challenged his mentor. He said the collapse was “serious, dramatic” but added that World War II and the 1917 Revolution were real catastrophes.

Medvedev also set himself apart 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 said. “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.”