A new round of Russian-U.S. arms control talks began Monday, and Russian military experts predicted they will not be easy, despite President Barack Obama's decision to scrap plans for an Eastern Europe-based missile shield that Moscow opposed.

Russian and U.S. diplomats are trying to negotiate a successor to the 1991 Strategic Arms Reduction Treaty, or START I, before it expires on Dec. 5. The agreement is seen as crucial for both nations to keep an eye on one another's nuclear stockpiles and also add credibility to their efforts to persuade countries such as Iran and North Korea to abandon their nuclear programs.

As talks got under way in Geneva, retired Maj.-Gen. Vladimir Dvorkin said Obama's decision to dump the Bush-era plan for missile defense installations in Poland and the Czech Republic removed a major stumbling block. Russian officials had vociferously opposed the plan, claiming it was meant to weaken Russia.

But Dvorkin, the former head of a military think-tank that developed Moscow's strategy in arms control talks, said that their differences are yet to be resolved.

Moscow and Washington have been arguing about which weapons will be subject to cuts, what will be the rules for counting nuclear warheads and how intrusive inspections of military facilities could be, Dvorkin told a news conference in Moscow.

"Negotiations aren't going easily," said retired Col. Gen. Viktor Yesin, the former chief of staff for the Russian military's Strategic Missile Forces.

He told the news conference that Moscow wants an end to intrusive U.S. inspections at the main Russian missile factory in Votkinsk, 1,000 kilometers (600 miles) east of Moscow, while the U.S. wanted to continue them.

"There are still many obstacles negotiators have to deal with," Yesin said.

The latest round of talks on a successor to START were expected to continue until Oct. 2, U.S. officials said.

Even if the parties fail to reach agreement quickly enough for the deal to be ratified before START expires, they may begin observing terms of the new deal immediately, Dvorkin said. "Nothing horrible will happen if the deal isn't ratified by Dec. 5," he added.

Dvorkin said that Obama's move to scrap the missile shield in Eastern Europe has created favorable conditions for prospective Russian cooperation with the United States and NATO on joint missile defense. "If we do that, it will be even more important than START," he said, adding that cooperation on a missile shield would dramatically boost mutual trust.

The latest call for pooling efforts in missile defense came from NATO Secretary-General Anders Fogh Rasmussen. On Friday, he urged the U.S., Russia and NATO to consider linking their missile defense systems against potential new nuclear threats from Asia and the Middle East.

The Russian Foreign Ministry welcomed Rasmussen's remarks, but said in a statement Monday that prospects for Russian-NATO cooperation on missile defense will depend on the U.S. administration's new approach to missile defense in Europe.

It remains unclear whether Moscow will make any significant concessions to Washington in response to Obama's move.

Russia's Deputy Defense Minister Vladimir Popovkin said Saturday that Russia will scrap a plan to deploy short-range missiles to the Kaliningrad region near Poland in response to Obama's decision to dump the missile shield in Eastern Europe.

But on Monday, the chief of the Russian military's General Staff, Gen. Nikolai Makarov, said that a "political decision" on the potential deployment of Iskander missiles is yet to be made by President Dmitry Medvedev.

The confusion appeared to reflect the Kremlin's annoyance with Popovkin for making the announcement, rather than hesitation about the issue. "Such important statements can't come from a low level," Dvorkin said.

Medvedev had threatened to order the deployment of Iskanders in Kaliningrad, if the U.S. pushed ahead with plans for missile-defense installations in Poland and the Czech Republic.