A modified rocket streaks across the sky during a test for the US missile defense system September 3, 2007. US interceptors in Poland would be fast enough to hit Russian ICBMs, a US researcher said Thursday. [AFP]

WASHINGTON -- Interceptor missiles deployed in Poland as part of a US missile defense shield would be fast enough to target Russian intercontinental missiles, contrary to US assurances, a US researcher said Thursday.

Ted Postol, a professor at the Massachusetts Institute of Technology and a long time critic of the US missile defense system, said the US Missile Defense Agency (MDA) is understating the speed of the interceptor and overstating the speed of Russian long range missiles.

MDA spokesman Rick Lehner said Postol had no access to missile test data and his assertions were "totally false."

The United States is negotiating to station 10 interceptor missiles in Poland and a high powered targeting radar in the Czech Republic to counter what it says is a growing missile threat from Iran.

Russia has objected vehemently to the plan on grounds that the European site could be used against its missiles, despite repeated denials from Washington.

Postol said the Americans "were probably concerned the Europeans wouldn't accept (the plan) so they came up with the false argument that the interceptors won't be fast enough to engage Russians' ICBMs."

He argued that the interceptor missiles would have to be faster than acknowledged by the Missile Defense Agency to be effective against missiles from Iran.

"The MDA claims the interceptors have a rather slow burnout speed, because you have to have a low burnout speed in order to not overtake Russian ICBMs," he said at a press conference.

"They claim a 6.3 kilometers per second speed. At this speed, the interceptor wouldn't be able to engage an ICBM from Russia," he said.

"But in fact, the burnout speed of this interceptor is closer to nine kilometers per second, which tends to fit to claims of the MDA that the system can protect from an Iran attack," he said.

"If the speed is inferior, then they can't defend places that they said they could defend earlier," he said.

Lehner insisted, however, that the US interceptors are not fast enough to catch a Russian ICBM.

"These missiles are more like six kilometers per second or a little more and it is certainly not sufficient to intercept a Russian missile, even coming out of a western part of Russia," he said.