* Serbia, Kosovo presidents meet in Brussels
* Better relations crucial for EU aspirations
BRUSSELS, Feb 6 (Reuters) - The presidents of Serbia and Kosovo pledged in Brussels on Wednesday to work towards mending their strained relations after holding the highest-level meeting since the former Serbian province seceded in 2008.
European Union foreign affairs chief Catherine Ashton, who has mediated between Belgrade and Pristina, held the brief talks with Serbia's Tomislav Nikolic, once an advocate of the Greater Serbia policy that fomented the Yugoslav wars of the 1990s, and Atifete Jahjaga of majority-Albanian Kosovo.
Discussions focused on cooperation, in particular in Serb-populated northern Kosovo, a main concern for the EU.
"Both have assured me of their continued support and commitment to the dialogue and their respective European agendas," Ashton said in a statement. "We are now tackling the issue of northern Kosovo and the coming weeks will be critical."
The EU is pressing both sides to mend ties five years since Kosovo declared independence from Serbia, before the bloc moves ahead with Serbia's bid to join.
The main talks involve the prime ministers of Serbia and Kosovo, who will meet again later in February.
Serbia lost control over Kosovo in 1999 after NATO-mounted air war against Serbian military and police forces accused of trying to purge Kosovo of ethnic Albanians to put down the uprising.
It refuses to recognise Kosovo's sovereignty, which is backed by over 90 countries including the United States and most EU members.
Nikolic reiterated Belgrade's position after the meeting.
"If Pristina's position stays firm, that they are an independent state, then we will hardly reach an agreement," he told reporters. (Additional reporting by Oliver Denzer and Ethan Bilby; Reporting by Justyna Pawlak; Editing by Angus MacSwan)