The Catalan club have closed the gap on league leaders Real Madrid to just four points in recent weeks.
Despite their first-leg tie at Chelsea on the horizon, Guardiola feels that his team's domestic duties are currently more important.
"I'll playing what I think is the strongest team that can adapt best to the opponent and the ground," he told reporters. "We know it's difficult but we want to extend our league challenge and to do that we have to play the best team we can.
"If the difference was 10 points we could make one competition a priority, but given the situation we are in, the game with Levante is more important."
Once Barca have finished their match in London on Wednesday, they will then turn their attentions to their league clash at home to bitter rivals Real Madrid on Saturday, April 21.