BRUSSELS (AFP) - EU leaders agreed Thursday to sign an association accord with Ukraine before the ex-Soviet state holds elections in May, European Union president Herman Van Rompuy said after an emergency summit on the crisis.

Van Rompuy said the 28 leaders reiterated the EU's commitment to signing the pact, whose rejection by pro-Russian ex-president Viktor Yanukovych triggered the protests that swept him from power last month.

"We decided that as a matter of priority we will sign very shortly the political chapters" of the accord, he said.

"This means before the Ukrainian elections of 25 May." The pact ditched by Yanukovych in November covered both a political accord with Brussels and a separate trade agreement to promote commercial links.

Brussels has insisted since then that the deal remained on the table but following Yanukovych's ouster and formation of an interim Kiev government, it had been cautious as to when it could be signed.

The European Commission, the EU's executive arm, initially suggested that it would wait until after the polls when a new government with a new mandate took office.

As the situation deteriorated following Russia's intervention in Crimea, there was growing pressure for a gesture of support for Kiev.

EU leaders Thursday also agreed to suspend visa liberalisation and other talks with Russia and threatened tougher measures if Moscow does not reverse course.