Chelsea have signed Portugal midfielder Tiago Mendes from Benfica on a three-year deal, the English premier league club said.

The 23-year-old completed a medical on Monday and will be part of a 23-man squad flying out to the United States later on Wednesday for a pre-season tour.

Chelsea did not reveal the transfer fee, which has been put at 10 million pounds by British media reports.

It would take Chelsea's spending on players since Russian billionaire Roman Abramovich took over the club in July 2003 to around 190 million pounds.

A member of the Portugal squad that reached the Euro 2004 final, Tiago signed late on Tuesday night, hours after Chelsea completed the signing of Ivory Coast striker Didier Drogba from Olympique Marseille for an estimated 24 million pounds.

Tiago is Chelsea's fourth recruit under new Portuguese manager Jose Mourinho after Drogba, Serbia and Montenegro striker Mateja Kezman and defender and Portugal team mate Paulo Ferreira.

Chelsea, who agreed deals before Mourinho's appointment for Dutch winger Arjen Robben and Czech keeper Petr Cech, are looking to improve on last season's runners-up slot in the premier league under former boss Claudio Ranieri.

Hours before completing the deal for Tiago, Mourinho had told reporters he was looking for a midfielder and a central defender to complete his squad for 2004-05.

The search for a defender could well be called off as the Portuguese coach has frequently said he did not want to sign any more players after leaving for the U.S. tour, where his side will face Celtic, AC Milan and AS Roma.