Ukraine's interim leadership pledged to put the country back on course for European integration now Moscow-backed Viktor Yanukovych had been ousted from the presidency, while the United States warned Russia against sending in its forces.

As rival neighbors east and west of the former Soviet republic said a power vacuum in Kiev must not lead to the country breaking apart, acting president Oleksander Turchinov said late on Sunday that Ukraine's new leaders wanted relations with Russia on a "new, equal and good-neighbourly footing that recognises and takes into account Ukraine's European choice."