(CNN) -- Cervelo's Xavier Tondo won the toughest stage of this year's Paris-Nice cycling classic as Alejandro Valverde finished second to ratchet up the pressure on race leader and their fellow Spaniard Alberto Contador.
It was the biggest victory of Tondo's fledgling career and reward for a solo break with just under 40km remaining of the 220km ride from Peynier to Tourrettes-super-Loup.
The whittled down chasing bunch closed fast in the final kilometers but Tondo had five seconds to spare with Valverde leading the charge to claim six bonus seconds.
It left him 14 seconds adrift of reigning Tour de France champion Contador ahead of a difficult final day in the south of France.
Young Slovakian Peter Sagan, who claimed his second stage win of the race in dramatic style pm Friday, finished third to retain the green jersey of points leader.
Tondo was delighted to win in his debut year for Cervelo, with his main duties this season set to be as a helper for Carlos Sastre in the Giro d'Italia and other major tours.
He felt he was ready to challenge on Friday, but suffered bad luck with a mechanical problem, dropping over two minutes to lose his chance for the overall crown.
"It gave me a chance to go in the breakaway today and I felt very good on the climb," he told the official Web site www.letour.fr.
"It's incredible for me, in my first year with Cervelo. It's my 10th victory as a pro, but in the past I only rode for small teams," he added.
Sunday's final leg is a 119km stage based around Nice with several tough climbs where Contador has predicted he will seal his final victory.
Meanwhile, last year's winner Michele Scarponi claimed the fourth stage of the Tirreno-Adriatico to take the overall lead.
Scarponi was in a small elite group who forged clear about 4km from the finish of the 243-km route from San Gemini to Chieti.
He now leads Benoit Vaugrenard of France by 18 seconds in the overall classification.