The US on Tuesday accused Russia and China of raising the risk of conflict in space, notably by developing anti-satellite weapons, as diplomats held talks on a treaty to keep space peaceful.
The closed-door negotiations in Geneva involving experts from 25 governments -- including the US, China and Russia -- are aimed at laying the groundwork for a legally-binding text to prevent an arms race in outer space.
Beijing and Moscow pushed for the discussions that run through March 28, which experts have said may show results despite the grim climate for disarmament diplomacy.
But addressing the United Nations Conference on Disarmament, US assistant secretary of state Yleem Poblete questioned whether China and Russia were sincerely committed to the talks.
"How can we believe (Russia is) serious about preventing an arms race in outer space when they are the ones that are developing ground-launched anti-satellite weapons?" Poblete asked.
She also accused Russia of trying to develop lasers that could "blind or damage satellites".
Poblete, of the State Department's arms control bureau, spoke as the US took over the rotating presidency at the Conference on Disarmament. The space peace talks are being held in a different venue in Geneva.
- China criticised -
Turning to China, Poblete accused the country of developing a range of anti-satellite capabilities, including jammers and ground-based missiles intended to target "low-Earth-orbit satellites".
Given that, "it is difficult to determine the truthfulness of China's concern about the prevention of an arms race in space," she said.
US President Donald Trump has called for the creation of a new military branch devoted exclusively to space, with the Pentagon submitting a proposal to Congress earlier this month.
Trump's "Space Force" call and his declaration that Washington considered space a "war-fighting domain," has raised widespread concern.
But experts have noted that the three major powers -- and all seafaring nations -- have a lot to lose if the ongoing negotiations collapse, given the increasing importance of satellite technology in both civilian and military affairs.
The negotiations being led by Brazil's ambassador to the Conference on Disarmament, Guilherme de Aguiar Patriota, will only produce a report if all nations reach consensus on its content.
He said he hopes the sides will agree on "elements" that could form the basis of a future, legally-binding treaty.