The United States on Wednesday accused China and Russia of working together to create a new 'profoundly illiberal' world order of which Moscow's actions towards Ukraine were just a part.

U.S. State Department spokesman Ned Price said every responsible country in the world, including China, had an obligation to urge Russian President Vladimir Putin to back down and de-escalate the Ukraine crisis.

"You will have to ask the PRC whether they have used their own considerable influence with the Russian Federation to that end," Price said at a regular news briefing in reference to the People's Republic of China.

Referring to an upgraded "no limits" partnership that China and Russia announced this month in which they pledged to collaborate more against the United States and the West, Price said the direction of the development of China-Russia relations was of "great concern."

"We think that Russia and the PRC also want a world order," he said. "But this is an order that is and would be profoundly illiberal, an order that stands in contrast to the system that countries around the world ... have built in the last seven decades.

"It is an order that is in many ways destructive, rather than additive."

Price noted that China had repeatedly in its statecraft stressed that the principal of sovereignty was inviolable and sacrosanct.

"So, you'll have to ask the PRC, how they marry that long-standing position with anything less than an effort to use the considerable influence and sway they have with the Russian Federation to urge Vladimir Putin to back down and to de-escalate," he said.

Ukraine declared a state of emergency on Wednesday and Moscow said separatists in the east had asked for help to repel "aggression" as the United States stepped up efforts to deter an all-out Russian invasion by imposing fresh sanctions.

China has urged all parties in the Ukraine standoff to exercise restraint and said that the sovereignty, independence and territorial integrity of any country should be respected and safeguarded.

At the same time, it has urged the United States to respect and address Russia's demands for security guarantees.

U.S.-based analysts say China is concerned about the impact Russian actions towards Ukraine could have on its trade relationship with Europe if it is considered to be supporting Russia.

But they also believe Beijing's ambiguous stance and its upgraded pact with Russia have given Putin the confidence to press ahead on Ukraine.

Experts told Reuters last week China would back Russia diplomatically and perhaps economically if it invades Ukraine, but would stop short of providing military support.

Washington has warned Chinese firms they would face consequences if they sought to evade any export controls imposed on Moscow in the event of Russia invading Ukraine.