Ukraine interim prime minister Arseniy Yatsenyuk put his country firmly in the Western camp Friday, signing the political provisions of a landmark association accord with EU leaders in defiance of Russia.

"This gesture symbolizes the importance both sides attach to this relationship ... and the joint will to take it further," EU president Hermann Van Rompuy said.

The EU was offering Ukraine its "steadfast support," Van Rompuy said, promising help to get the country's struggling economy back on track.

"We are sure that together we will succeed," Yatsenyuk said after the European Union's 28 heads of state and government signed their names to the deal.

The accord, years in the making, was suddenly ditched by Ukraine's pro-Kremlin president Viktor Yanukovych in November. It was this that sparked protests leading to his fall last month, setting off the worst East-West crisis since the end of the Cold War.

The political provisions of the 'EU-Ukraine Association Agreement' cover shared democratic values, improved economic ties, judicial reform and other aspects of civil society.

Europe's leaders have agreed to press ahead with signing the full accord and an accompanying free trade agreement, likely after Ukraine elections on May 25, as they seek to bolster Kiev against a newly-assertive Russia.

As if on cue with Friday's signing, Russia's upper house of parliament voted unanimously to ratify the treaty incorporating Crimea into Russia, following a similar vote Thursday in the lower house.

The annexation of Crimea saw the EU join the United States Thursday in imposing sanctions on high-ranking Russian figures.

President Barack Obama blacklisted 20 Russian lawmakers and senior government officials, in addition to 11 already targeted, and warned Moscow faced international isolation if it did not reverse course.

(AFP)