A top US official told the global disarmament body in Geneva that Washington had no confidence in the draft Treaty on the Prevention of the Placement of Weapons in Outer Space and of the Threat or Use of Force against Outer Space Objects, or PPWT.

US Assistant Secretary of State for Arms Control, Yleem D. S Poblete, said the US was committed to strengthening the safety, stability and sustainability of space.

But she insisted "the draft PPWT is not the right mechanism for accomplishing that".

"Hollow and hypocritical efforts are not the answer," she said, maintaining that the PPWT, first presented by Russia and China in 2008, was "a flawed document".

The accusation came as the US eyes creating a Space Force as a new military branch, something President Donald Trump has said would give his country dominance over its rivals.

Russia's representative at the Conference on Disarmament hinted Poblete's criticism of the PPWT might be a smokescreen to divert attention from that project.

"Every time they want to hide intentions, diplomats draw attention to other issues," he said.

- 'Extremely flawed' -

Both he and his Chinese counterpart insisted on the good intentions of the draft treaty and urged Washington to collaborate on a text everyone could agree on.

In a heated back-and-forth with the Russian diplomat, US Ambassador Robert Wood insisted the PPWT was "extremely flawed" and beyond repair.

Poblete meanwhile said she was particularly wary of the Russia-backed draft treaty, given "the recent pattern of Russian malign behaviour".

She accused Moscow of "actively pursuing the development and deployment of anti-satellite weapons", and voiced concern over observations of "strange" behaviour by Russian satellites.

"What Russia tells us diplomatically and publicly may be the opposite of what it intends to do with that satellite," she said, pointing for example to the "very abnormal behaviour" of a "space object" deployed by Russia last October.

"The PPWT's proponents, through very careful parsing of treaty language, would allow the very activities they claim to prohibit," she insisted.

Trump ordered the creation of Space Force in June, arguing the Pentagon needs it to tackle vulnerabilities in space and assert US dominance in orbit.

Its creation, however, is not a done deal, as it needs approval from Congress, and the concept has met scepticism from lawmakers and defence officials wary of the cost and added bureaucracy.

But Vice President Mike Pence last week was unequivocal in presenting the administration's wish for it to become a reality -- preferably by 2020, the end of Trump's term in office.