China and Russia are seeking to update the 1967 Outer Space Treaty, which, in its new form, would serve to hinder the US's space capabilities and ambitions.

This February, China and Russia introduced a draft treaty entitled the 'Prevention of Placement of Weapons in Outer Space' at the 65-member UN Conference on Disarmament in Geneva.

The two countries reiterated their support for the new accord in late May during a summit in Beijing, saying: "The sides are in favour of the peaceful use of space, but are against the deployment of weapons in space or a space arms race."

Although the concept of a new agreement has support among some arms-control advocates, the Bush administration rejected the notion of a treaty, concerned about limitations on the United States' access to, and use of, space.

The White House is right - and it is a policy that should be carried through to the next US administration.

Currently, the issue falls under the 1967 Outer Space Treaty, which bans the deployment of 'weapons of mass destruction', but not conventional weapons, in space. It also forbids military facilities, weapon testing or manoeuvres on the Moon or other celestial bodies.

However, the current Sino-Russian attempt to expand the 41-year old treaty has a slew of shortcomings. For instance, it disallows the deployment and testing of space weapons, but incredibly does not ban their research and development or production.

This huge lacuna runs the risk of allowing, even encouraging, the development of a potential counter-space 'breakout' capability - that is, a clandestine but untested anti-satellite (ASAT) system - while still remaining inside the treaty's limits.

Moreover, in view of China's direct-ascent ASAT test in January 2007, this new treaty would only serve to bridle US space capabilities, while giving the Chinese and Russians ample opportunity to close the technological gap.

Indeed, considering their great power ambitions, it is feasible that Beijing or Moscow would deploy space weapons today if they could; the treaty could merely be a diplomatic gambit to buy time to develop their own counter-space programmes.

To this end, a US official recently told a congressional commission that Chinais "aggressively" developing abilities to target satellites with (undeclared) space and counter-space assets.

Other analysts are also concerned that Moscow and Beijing are trying to put the brakes on the possible development of a space-based missile defence system, too, which has been considered. (This concept may be given a re-look in view of Iran's most recent round of missile testing and the basing problems that have befallen missile defence systems in Eastern Europe.)

In addition, there are other worries such as the definition of a 'space weapon'. While this may seem basic, in theory a satellite could be used to attack another satellite simply by ramming it - making it, in essence, a weapon.

Moreover, systems with real counter-space capabilities could escape restriction, or even be included to the detriment of other civilian space programmes, such as when the Soviets tried to 'capture' the US Space Shuttle as a 'space weapon' during the Carter administration.

Another concern is verification. The terms of the treaty must provide for transparency, ensuring compliance with the accord - and discouraging the establishment of a secret arsenal of ASAT weapons.

Furthermore, a tremendous amount of time, effort and cost would be required to inspect every space payload. (This does not even begin to take into account the risk of espionage against sensitive space-launch vehicle and satellite systems.)

And what about terrestrially based systems, including direct-ascent, radio-frequency and directed-energy weapons, which are the future wave of counter-space capabilities, especially as regards the Chinese? The Pentagon annual report on Chinese military power cites Beijing's involvement in both kinetic and non-kinetic counter-space programmes.

In fairness, the Chinese and the Russians have admitted the challenges of implementing such an agreement. In fact, some Conference on Disarmament states are insisting on a discussion of the Chinese ASAT test before agreeing to consider the draft treaty.

Treaty detractors point out the US has the most to lose in any new agreement. As a leading space power, the US (and its friends and allies) would be relinquishing much more strategic advantage than China or Russia- for the moment, at least.

No nation relies more on space than the US. Space is the ultimate military high ground and critical to maintaining the ability of US armed forces to meet its security commitments to friends and allies around the globe.

Potential adversaries know this, seeing space as the US's Achilles' heel. As the US Director of National Intelligence noted to Congress this year: "Over the last decade, the rest of the world has made significant progress in developing counter-space capabilities."

Beijing and Moscow are looking to challenge Washington for pre-eminence in space. Both likely believe that if they have the capacity to hold US space assets at risk, Washington will be increasingly reluctant to challenge them militarily.

Protecting US space assets - and freedom of action on the high frontier - must be central to US national security. A failure to maintain space superiority would not only invite a debacle in space for the US - but for its friends and allies, too.

Peter Brookes is a senior fellow at the Heritage Foundation - a US policy think-tank - and a former US deputy assistant secretary of defense