WASHINGTON - The United States plans to let a landmark nuclear arms reduction treaty with Russia expire in 2009 and replace it with a less formal agreement that eliminates strict verification requirements and weapons limits, a senior US official says.

A serviceman passes by an opened SS-18 intercontinental ballistic multiple-warhead Satan missile launching silo in the town of Kartaly, in Russia's Chelyabinsky region, in this August 16, 2002 file photo. [Reuters]

This would continue President George W. Bush's practice of repudiating arms control as a means of curbing nuclear weapons while relying more on countermeasures like export controls, interdiction and sanctions.

Related readings: World's 1st floating nuclear power plants under construction Russia launches new generation nuclear submarine Russia sees civil nuclear deal with US in '07 US, Russia reach nuclear arms deal

This approach makes many arms control experts uneasy, but the Democratic-led US Congress has shown little interest in the START treaty's fate. Some congressional aides say whatever Bush does, his successor - who takes office in January 2009 - could seek modifications.

While the Strategic Arms Reduction Treaty or START "has been important and for the most part has done its job," Assistant Secretary of State Paula DeSutter told Reuters the pact is cumbersome and its complicated reporting standards have outlived their usefulness.

In the post-Cold war era, many provisions of the 1991 START accord, which mandated deep nuclear weapons cuts, "are no longer necessary. We don't believe we're in a place where we need have to have the detailed lists (of weapons) and verification measures," added DeSutter, who handles arms control and verification issues.

Russia agrees the treaty should not be extended but wants it replaced with another legally binding treaty that makes further cuts in strategic forces, so the two sides have significant differences.

2007 TARGET

DeSutter said concluding a START replacement pact by year's end is "one of my top priorities."

START obligated Moscow and Washington to slash deployed strategic nuclear forces from approximately 10,000 warheads each to no more than 6,000 apiece by December 5, 2001. The accord also limits each side to 1,600 delivery vehicles, like intercontinental ballistic missiles.

As of January 1, Russia reported 4,162 warheads under START, and the United States claimed 5,866 warheads but these figures are not exact because of unique treaty counting rules.

Another pact, the May 2002 Strategic Offensive Reduction Treaty (SORT), commits the two sides to reduce forces to 1,700-2,200 operationally deployed warheads by the end of 2012.

Daryl Kimball of the Arms Control Association said the two sides should have less than 1,500 warheads each. Asked if Washington could accept such a target, DeSutter said: "Not at this point."

Experts say the US intelligence community is worried about losing the extra insight into Russia's arsenal, beyond satellite imagery, that START verification rules provide.

But DeSutter said verification provisions, like onsite inspections, have not always worked well, with Russia sometimes hiding weapons from US view.

Verification is highly intrusive and expensive "but you're never going to know how many warheads they are going to have on various missiles," DeSutter said.

Despite US-Russian tensions over missile defense, Washington does not see Moscow as an enemy and believes there are other ways to ensure transparency in their respective nuclear and military capabilities, she said.

Sen. Joseph Biden, Democratic candidate for president and Senate Foreign Relations Committee chair, said: "It's a lose-lose situation for the US and Russia if START were to lapse. The last thing US or Russia needs is another arms race and the START treaty helps ensure we never head down that path again."