For the agreement to come into force, EU members' parliaments need to ratify the document which political scientists say could be difficult.
In November 2007, the EU and Serbia initialed the agreement, and Serbia ratified it, but Belgrade has failed to implement all Brussels' demands concerning handing over those Serbs wanted by the UN war crimes tribunal, including Ratko Mladic, a Bosnian Serb army chief, accused of ordering the massacre of around 7,000 Bosnian Muslims in 1992-95.
The EU is concerned nationalist groups opposed to closer ties with the EU could win May 11 parliamentary elections.
Serb premier Vojislav Kostunica has spoken against the new agreement and said the new government will annul the decision once it wins the elections.
"Serbia's new government and parliament will annul the unlawful signing by [pro-Western President Boris] Tadic. We will never let anyone sign Kosovo's independence on Serbia's behalf and that's why today's signature means absolutely nothing," Kostunica said.
Kosovo, with a 90% ethnic-Albanian majority, has been formally recognized as a sovereign state by over 35 countries including the U.S. and most EU members since it proclaimed its independence from Serbia on February 17. Russia and China continue to back Belgrade's position that Kosovo will always remain a part of Serbia.
Ex-Soviet breakaway regions have stepped up their drive for self-rule since Kosovo's declaration.
