ATHENS, Greece (AP) _ Greece's police chief urged English soccer fans not to travel to Athens for the Champions League final on May 23 unless they have a ticket.

About 20,000 officers will be deployed from greater Athens and other cities for the match in security measures similar to those used for the 2004 Olympics.

One English team is guaranteed to play the final. In the semifinals, Liverpool faces Chelsea and Manchester United plays AC Milan.

``We advise everyone who cannot get their hands on a ticket not to travel to our country,'' Lt. Gen. Anastassios Dimoshakis said Friday after a meeting for security chiefs and the mayor of Athens at the Greek Public Order Ministry.

``Security checks will start at airports, but also from the countries of origin of the fans,'' he added. ``We are already co-operating with all European police forces.''

Dimoshakis said police would try to keep rival supporters apart throughout their stay in Athens, and take steps to stop fans drinking excessive amounts of alcohol. He did not elaborate.

Security cameras at the Olympic Stadium will also be upgraded for the final. It is part of a campaign to tackle domestic hooliganism by introducing cameras and forcing fans to prove their identity when buying tickets.

All Greek professional team sports were suspended for two weeks after a fan was killed in March 29 clashes between supporters of soccer clubs Olympiakos and Panathinaikos.

Greek officers are working with British and Italian law enforcement agencies for the final. State-run NET television said a delegation of Greek officers would travel to Britain on Monday.

``The Greek police is exclusively responsible for providing security at the final, but we are also have active international co-operation,'' Public Order Minister Vyron Polydoras said.

``Our aim is ... to guarantee that sporting events (held in Greece) are peaceful.''

Security will also be heightened for the Euroleague final four basketball tournament in Athens from May 4-6.