Chelsea target Andre Villas-Boas has opened the way for a move to the English Premier League by resigning as FC Porto coach, the Portuguese champions confirmed on Tuesday.
Villas-Boas informed FC Porto that he was breaking his contract by paying a 15-million-euro ($21.35m) departure clause.
FC Porto said in a statement that they had been "notified of the intention of coach Andre Villas-Boas to terminate his contract by activating the departure clause with immediate effect".
The club added that the 33-year-old Villas-Boas' contract "would be terminated after the payment of the required sum".
Earlier Portuguese news agency Lusa reported that Villas-Boas informed the club by fax of his decision.
The payment of the departure clause would allow Villas-Boas to sign for Chelsea, without a coach since Carlo Ancelotti was sacked.
The Blues are seeking to replace Ancelotti, who was given the boot at the end of last season after failing to land any silverware, just 12 months after guiding the west London club to an historic double of league and FA Cup titles.
Porto president Pinto da Costa admitted on Monday the club could not prevent their manager from leaving if the required financial conditions were met.
"Villas-Boas has a contract and a clause of 15 million euros," he said.
"If someone deposits 15 million euros into our account and he wants to go, we cannot do anything because it is something that is contractually specified."
A former assistant to Jose Mourinho at Chelsea, 33-year-old Villas-Boas led Porto to three titles in his first season at the club: the Portuguese league title, the Portuguese Cup and the Europa League.
In doing so, he became the youngest coach to win a European trophy.
Although Chelsea made no official comment, reports suggest a £4.4m-a-year ($7.1m) salary is on the table for Villas-Boas, who could bring Porto's Colombian star striker Radamel Falcao to Stamford Bridge with him.
Turkey coach Guus Hiddink has also been linked with a return to Chelsea, where he won the FA Cup as a caretaker manager in 2009, as well as former Fulham, Manchester City and Blackburn Rovers boss Mark Hughes.
Porto were unbeaten in the league last season with 27 wins in 30 matches, becoming only the second Portuguese club to finish a league season unbeaten, after Benfica in 1972-73.