"This is an extremely gratifying moment for me. Without a doubt it will be good for my career and I am eager to start working and growing with my new colleagues," the 30-year-old told Lisbon-based news radio TSF.

Hilario will be the London club's third-choice goalkeeper behind Petr Cech and Italy's Carlo Cudicini.

He played under Chelsea's Portuguese coach Jose Mourinho at FC Porto in the 2002-03 season.

"I already worked with him and I know he is intelligent. It's necessary to be intelligent in order be a substitute to the best goalkeeper in the world," Mourinho told Portuguese television station TVI earlier this week.

Hilario's three-year contract with Nacional, based on the Portuguese island of Madeira in the Atlantic, was due to expire at the end of July.

Nacional finished the season in fifth place, securing a spot in the UEFA Cup alongside Sporting Braga and Portuguese Cup finalists Vitoria Setubal.