Footage has emerged of rightwing maverick Sarah Palin warning that if Barack Obama were elected to the White House then Russia would be likely to invade Ukraine.

In a 2008 presidential campaign speech, Palin details the various crises the US would have to confront should Obama be elected.

"After the Russian army invaded the nation of Georgia, Senator Obama's reaction was one of indecision and moral equivalence - the kind of response that would only encourage Russia's Putin to invade Ukraine next," said Palin.

Her comments were in response to Obama's current vice-president Joe Biden who warned Democrats that other world leaders would want to test the presidential candidate if he became president of the United States.

Russia has taken control of Crimea after Ukraine's president Viktor Yanukovich was ousted from power by anti-government protests.

Ukraine's first president, Leonid Kravchuk, slammed the invasion and warned of World War III. He said he would take up arms - despite being 80 years old - to defend his homeland if Moscow did not retreat.

Follow our live blog on developments in Ukraine here.