On the eve of an international conference on missile-defense, the U.S. is holding firm to its contention that a Europe-based system strongly opposed by Moscow presents no threat to Russia.

Russian officials plan to push the opposite view and the deputy defense minister warns that talks on the dispute could reach a point of no return.

The U.S.-led NATO plan to deploy missile defense elements in Europe is a top irritant in Moscow-Washington relations. Russia has called a two-day conference on the issue beginning Thursday with representatives from about 50 countries.

The U.S. says the system would stave off threats from rogue nations such as Iran. Moscow contends it would undermine Russia's nuclear forces.

"Our view and analysis is that the United States' missile defenses don't undermine Russia's strategic deterrent ... we will once again present the technical facts at this conference," U.S. State Department special envoy Ellen Tauscher said in a conference call Wednesday.

"I wouldn't say we're at a stalemate in any case. We know what the areas of concern and questions are, but because many of them are technical and some of them are political it's important that we continue these technical and expert conversations moving toward the opportunity for cooperation in the future," she said.

But Russia's deputy defense minister, Anatoly Antonov, told government newspaper Rossiiskaya Gazeta that Moscow will present new evidence bolstering its claim.

The conference's key "in my view, will be the presentation of the results of computer modeling demonstrating how the elements of NATO missile defense, among them new objects in Poland, Romania, Turkey and other places, can have influence on Russia's nuclear deterrent," he said in an interview published Wednesday.

The plans follow a "phased-adaptive" approach using Aegis radars and interceptors on ships and a more powerful radar based in Turkey in the first phase, followed by radars and interceptors to Romania and Poland. Russian officials have warned of retaliatory actions if the deployments threaten Russia; a Russian newspaper reported last month that advanced S-400 surface-to-air missiles have been placed in Kaliningrad, the exclave bordering Poland.

The Poland elements will be deployed in the third phase, estimated at 2018. Antonov characterized that as the point at which further negotiations could be impossible.

"When the Americans reach the third step of realizing their anti-missile plans in Europe and put the effectiveness of our strategic nuclear forces under threat, there will be serious questions regarding an adequate reaction by Russia," he said.

But Tauscher said, "We have made our commitment to our NATO allies and we have announced, the president has announced, the phased adaptive approaches and I will tell you there is nothing I can imagine that will stop us from making those deployments on time."

In any case, with the U.S. facing a presidential election in the fall, "I think it's pretty clear that this is a year in which we're probably not going to achieve any sort of a breakthrough," said Madelyn Creedon, the U.S. assistant defense secretary for global strategic affairs, who also will be at the Moscow conference.