Brussels - The United States formally joined the European Union's rule-of-law mission (EULEX) in Kosovo on Wednesday by offering 80 police officers and "up to" eight judges and prosecutors to the 3,000-strong operation, officials said.

"The European Union and the United States have a common desire to work together to support the development of Kosovo's democratic standards," a joint statement issued at a signing ceremony in Brussels read.

The two sides stressed the need to strengthen "an independent and multi-ethnic rule-of-law system" in the predominantly ethnic-Albanian enclave, which declared its independence from Serbia in February.

The EULEX mission has been bogged down by delays and is now not expected to become fully operational until December, instead of June as originally planned.

Once it is up and running, EULEX will flank a separate UN mission in supporting the Kosovo authorities by providing advice and training to the its police and judiciary.

Based in the capital Pristina, EULEX will count on 1,900 international police officers, judges, prosecutors and customs officials and about 1,100 local staff when it reaches full strength.

The mission budget totals 205 million euros (263 million dollars), covering a period of 16 months.

Its contributing countries include most EU member states, as well as Norway, Switzerland, Turkey and Croatia.

This is the first time that the US has participated in an EU security and defence policy mission. (dpa)