US National Security Adviser Susan Rice says Russia, Europe and the United States all have an interest in keeping crisis-hit Ukraine from breaking apart.
A new era dawned in the ex-Soviet state when parliament appointed a pro-Western interim leader after impeaching a defiant president Viktor Yanukovych, whose whereabouts remain a mystery following a week of carnage that capped three months of mostly peaceful protests.
"It's not in the interests of Ukraine or of Russia or of Europe or of the United States to see the country split," Rice told NBC's Meet the Press talk show.
"It's in nobody's interest to see violence return and the situation escalate."
She warned it would be a "grave mistake" for Ukraine's old master Russia to send in forces to restore the kind of government it would like to see in Kiev.
"There is not an inherent contradiction... between a Ukraine that has long-standing historic and cultural ties to Russia and a modern Ukraine that wants to integrate more closely with Europe," Rice said.
"It need not be mutually exclusive."
In a phone call with his Russian counterpart Sergei Lavrov, US Secretary of State John Kerry "underscored the United States' expectation that Ukraine's sovereignty, territorial integrity and democratic freedom of choice will be respected by all states".
According to a senior State Department official, Kerry also expressed Washington's "strong support" for the Ukrainian parliament's move to name an acting president and acting prime minister.
Treasury Secretary Jacob Lew, meanwhile, pointed to "broad support" at the G20 meeting in Sydney for an international aid package based out of the International Monetary Fund, once a transitional government formally takes power.
