Munich, Dublin and Bilbao are all at risk of losing games at Euro 2020 with the three cities given a Friday deadline by UEFA to confirm their ability to host fixtures at the tournament this summer, sources have told ESPN.

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The 24-team competition, delayed by 12 months due to the coronavirus pandemic, is due to start on Jun 11 when Italy face Turkey in Rome (stream Euro 2020 matches in the U.S. on ESPN+).

But the format of the pan-European tournament, which is scheduled to be staged in 12 cities across the continent, is still to be finalised by UEFA because of the inability of those three sites to guarantee they can host games in front of spectators at stadiums.

Sources have told ESPN that Dublin is almost certain to withdraw as a host this week as a result of the Irish government's reluctance to compromise its COVID protocols in order to allow fans to attend games at the Aviva Stadium, which had been scheduled to stage four fixtures including a round of 16 tie.

UEFA has yet to identify a back-up venue to stage Dublin's games, although sources have said that sites in England, Scotland and Russia are under consideration.

Spanish city Bilbao is also likely to surrender its four fixtures -- three Spain group games and a round of 16 tie -- due to local COVID issues in northern Spain.

However, sources have said that the southern Spanish city of Seville is likely to step in as host if UEFA can be convinced that the 60,000-capacity Estadio de la Cartuja -- which staged the 2003 UEFA Cup Final between FC Porto and Celtic -- is a suitable alternative. The home stadiums of Sevilla FC and Real Betis are not being considered.

The potential loss of Munich as a venue is causing greatest concern to UEFA, however, with the Allianz Arena due to host three Germany games, including the eye-catching fixtures against France and Portugal, and a quarterfinal tie.

COVID regulations in Germany currently prohibit fans inside stadiums and UEFA has yet to receive assurances that the position will change in time for the start of Euro 2020.