The United States is about to lose a key arms-control tool from the closing days of the Cold War -- the right to station American observers in Russia to count the long-range missiles leaving its assembly line.

The end of full-time, on-site access will likely ignite complaints in Congress, with insiders from both parties arguing over whether the George W. Bush or the Obama administration is responsible.

Republicans are worried by the previously undisclosed agreement between the Obama administration and the Kremlin in October, which formalizes the inspectors' departure this Saturday. This, they warn, would cripple Washington's ability to police Moscow's compliance with agreed reductions in its nuclear arsenal.

Democrats, on the other hand, insist they were "stuck" with an agreement reached late last year between the Bush administration and Moscow but not made public. This, they said, left the Obama team no choice.