Chelsea have reached an agreement with Ajax to sign the Dutch winger Hakim Ziyech this summer for a fee of 40m Euros.
The 26-year-old was a January transfer target for Chelsea boss Frank Lampard.
Ajax were unwilling to sell the Morocco international in the transfer window as they chase the Eredevisie title.
The signing is the first by Lampard following Chelsea's transfer ban.
The Premier League side were linked with a number of signings in January, including Paris Saint Germain forward Edinson Cavani and Napoli striker Dries Mertens.
Chelsea will play Manchester United in the English Premier League at 8am next Tuesday.
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