The United States pressed Ukraine yesterday to free the jailed ex-premier Yulia Tymoshenko as she entered the 12th day of a hunger strike that may prompt an EU boycott of its Euro 2012 football games.

US Secretary of State Hillary Clinton’s statement pushed Ukraine into still further diplomatic isolation just weeks before it begins co-hosting with Poland a tournament watched by billions across the world.

European football authorities conceded they were facing growing calls to either move or postpone the once-in-four-year event when it kicks off in co-host nation Poland on June 8 before concluding with the final in Kiev on July 1. But they said a venue switch at this late juncture was impossible despite fears of a humiliating no-show by European leaders to any of the matches played in the four Ukrainian host cities.

Mrs Clinton said Washington was “deeply concerned by the treatment” of the 2004 Orange Revolution leader and pressed for the release of her and “the other members of her former government” jailed since they lost elections in 2010. Yet Mrs Clinton also expanded her earlier demands by additionally calling for “the restoration of their civil and political rights” – a move that could make Ms Tymoshenko into a future election threat to President Viktor Yanukovych.

Ms Tymoshenko was jailed for seven years in October in a highly controversial case that immediately damaged Ukraine’s relations with the EU.