U.S. plans to deploy a missile defense system in Eastern Europe continue to be a major source of contention between the United States and Russia. In this report from Washington, VOA Senior Correspondent André de Nesnera looks at the latest statements by senior U.S. officials on the controversial defense system and how they are being interpreted.

U.S. officials say the proposed missile defense system - made up of 10 missile interceptors in Poland and a radar in the Czech Republic - is needed to defend against potential threats from countries such as Iran. They say it is not targeted against Russia.

But Russian officials have strongly criticized the proposed missile defense system.

Michael Levi, an arms control expert at the Council on Foreign Relations says there are two reasons behind Moscow's objections.

"The one that is expressed publicly is that the missile defense could threaten the Russian [nuclear] deterrent," he noted.  "There is very much a hollow ring to that. Russia's nuclear weapons could overwhelm anything the United States would deploy. The deeper concern that Russia presumably has, is that this deployment in Poland and the Czech Republic signals a deepening of relations between the United States and former Soviet satellites. That is what fundamentally is disturbing to Russia."

On Tuesday, during a speech to the National Defense University, President Bush repeated his administration's view that a missile defense system is necessary.

"The need for missile defense in Europe is real, and I believe it is urgent," said Mr. Bush.  "Iran is pursuing the technology that could be used to produce nuclear weapons, and ballistic missiles of increasing range that could deliver them."

Earlier in the day, speaking in the Czech Republic's capital, Prague, U.S. Defense Secretary Robert Gates appeared to set a softer tone, saying the U.S. missiles may not be activated immediately after being deployed.

"We have not fully developed this proposal," he said.  "But the idea was we would go forward with the negotiations, we would complete the negotiations, we would develop the sites, build the sites - but perhaps delay activating them until there was concrete proof of the threat from Iran."

Arms control experts are discussing whether President Bush and Secretary Gates sent out mixed signals.

Daryl Kimball, head of the independent Arms Control Association, says there is no disagreement between the two men.

"Superficially, it may appear as though there is some disconnect," he noted.  "But what Secretary of Defense Gates is saying is, and what President Bush is saying is that we want to move ahead and build the interceptor site in Poland, build the radar in the Czech Republic on our current schedule. What Gates is hinting at is that the 'on switch' will not be turned, until the United States and Russia agree that there is an urgent Iranian threat. They [Bush and Gates] are both saying that we should go ahead with building, or beginning to build these sites in 2009-2010, so they can be completed sometime around 2012 or 2013."

But Michael Levi, from the Council on Foreign Relations, says the statements do appear contradictory.

"The president describes the need for missile defense in Europe to be 'urgent.' Bob Gates talks about delaying activation of the missile defense sites until we actually saw what he calls 'definitive proof of the threat' - Iranian missile testing and so on, as he puts that," he said.  "Those appear to be contradictory. If a threat is urgent, then you do not talk about waiting for proof of that threat, for more knowledge of that threat."

Levi does not believe that either President Bush or Secretary Gates, or their spokesmen, would clarify their statements. He expects them to say that the missile defense system in Eastern Europe is part of a discussion with Russia, and leave it at that.