European Union leaders have reaffirmed their determination to continue the process of expansion while setting strict standards for candidate nations.

At the conclusion of their two-day summit in Brussels, the leaders stressed the need to reform the union's governing treaty and work on efforts to revive the EU constitution after its defeat by French and Dutch voters last year. European Commission President Jose Manuel Barroso expressed confidence for renewal of the process under Germany's presidency in 2007.

The leaders approved the decision of the bloc's foreign ministers to partially suspend Turkey's entry talks because of Ankara's failure to normalize trade with Cyprus. They stressed that Turkey and other candidates must fully comply with existing entry criteria.

Bulgaria and Romania will join the bloc January 1. But other candidates, including Croatia, Macedonia and Serbia, must wait until EU countries adopt structural reforms.

The leaders specifically mentioned the importance of Serbia's cooperation with the United Nations war crimes tribunal as a requirement for building EU ties.

On other matters, the leaders agreed to move against illegal immigration, strengthen the EU border patrol agency, and set up a coastal patrol force to prevent African illegal immigrants from reaching the shores of member states.

They called for strengthening the EU common energy policy and for joint efforts to deal with environmental challenges.

Some information for this report was provided by AP and Reuters.