The Catalan club looked out of the title race when they slipped 12 points behind Real Madrid last month.
But, while the leaders have dropped points against Malaga, Villarreal and Valencia in recent games, Barca have kept plugging away and last night [Saturday] clinched their 11th straight victory in La Liga to swiftly reduce the gap back to four points after Jose Mourinho's side had beaten Sporting Gijon 3-1.
Guardiola's side take on Roberto Di Matteo's Blues on Wednesday night in the first leg of their Champions League semi-final at Stamford Bridge, and the 41-year-old insisted his focus was on that rather than next Saturday night's Clasico at the Nou Camp.
"I don't have the strength to think about it [the match against Madrid]. We have to focus on Chelsea - it's a Champions League semi-final," he said on www.fcbarcelona.cat.
"If they win, it's over. We'll see how we come into the match. We'll have to play a very good game to beat them."
However, having previously said it would be "almost impossible" to catch Madrid, he acknowledged after last night's triumph: "It's a little less impossible."
The Spanish and European champions were forced to work hard before Lionel Messi's second-half double earned them victory at the Ciutat de Valencia.
Jose Barkero gave Levante the lead with a 23rd-minute penalty and Barca appeared to be making heavy weather of getting back on terms.
But Messi burst into life with two goals in nine minutes, the second a spot-kick of his own, to turn the game around.
Guardiola said: "They are one of the worst teams to have to fight back against. They are very well organised in defence. They have players with a lot of experience.
"Furthermore, they're fantastic on the counter. After the first goal, they went back [in their own half] to defend the result.
"It's clear that Levante have made it to where they are now because they've done a good job."
He added: "In the second half we opened up the field. Our objective was to score the first goal, but after conceding a goal, we had to change some things to win the match.
"[Isaac] Cuenca gave us width. Playing a goal down against these types of teams is very complicated, and if you lose the ball they kill you.
"We tried to attack with everything we had and in the end we managed to get a result that keeps us in it."