The Texas singer was photographed with a poster showing the logo for Red Card for Romania, set up by animal lovers to protest again President Traian Basescu's new policy to allow dogs in the capital Bucharest with no owners to be but down.
She follows in the footsteps of Brigitte Bardot who spoke out this week in her fight against the move. The 78-year-old French actresss-turned-animal-rights-activist called the president a "tyrant" for backing the law.
"This tyrant thinks only of killing, and I condemn his dictatorial policy, which is unworthy of a member of the European Union," she said. "You would think we had returned to the Ceausescu years."
The law allowing authorities to put stray dogs to sleep if they are not claimed within two weeks was passed earlier this week.
The president was expected to approve the measure, which Bardot termed " genocide".
The statute was passed a week after a child died after dogs bit him near a Bucharest park.
"It would be scandalous, unfair, to condemn all innocent dogs to death because of an isolated incident," Brigitte said.
Animal charity K-9 Angels has asked Paul O'Grady, presenter of ITV's For the Love of Dogs, to back its campaign to save Romania's stray dogs.