Germany Under-21 captain Lewis Holtby on Monday quit Bundesliga side Schalke 04 to join Premier League team Tottenham Hotspur, the north London club confirmed.
"We are delighted to announce that we have reached agreement with Schalke for the immediate transfer of Lewis Holtby," Spurs said in a statement.
With his Schalke contract to expire in June, the 22-year-old had already committed to joining Spurs for next season having signed until 2018, but the two clubs have agreed a deal to take the midfielder to England immediately.
Schalke's general manager Horst Heldt met Spurs chairman Daniel Levy in London over the weekend to finalise the transfer which is reported to be worth 1.75 million euros (Â£1.50 million, US$2.35m).
Holtby's replacement, 29-year-old Brazil midfielder Bastos, will undergo a medical check in Gelsenkirchen on Monday and is set to join on loan from French first division side Lyon with an option to buy, according to German daily Bild.
Schalke face Turkey's Galatasaray in the Champions League's last 16 on February 20 in Istanbul and are currently sixth in the Bundesliga.
So far this term Holtby has scored four goals in 27 appearances for Schalke.
He joined Schalke in 2009 from Alemannia Aachen and was loaned out to Bochum and Mainz prior to making his breakthrough with the Gelsenkirchen-based club.
In his professional career, Holtby has scored 29 goals in 160 appearances.
Reports in Britain said Holtby will move to London from Germany at the weekend, ruling him out of Tottenham's matches against Norwich and West Brom on Wednesday and Sunday respectively.
Tottenham, knocked out of the FA Cup by second-tier Leeds on Sunday, are currently fourth in the Premier League and pushing for a place in next season's Champions League.