The 21-year-old defender returns to the Camp Nou stadium four years after moving to Man United. He agreed to a four-year contract, with Spanish media reporting the transfer was 5 million (US$8 million).

"It's a dream to return to Barcelona. When I left I thought it would be very complicated to return and now the dream has come true," Pique said.

Pique came up through the ranks of Barcelona's youth system - alongside players such as current striker Bojan Krkic and Arsenal midfielder Cesc Fabregas - before Man United signed him in 2004.

The Spain under-21 player made the Red Devils' first team this season after spending the last one on-loan at Spanish club Zaragoza.

Playing time was hard to come by for Pique, who scored two goals in 23 games with United.

"Although Pique enjoyed his most prominent Old Trafford season during 2007-08, the long-standing central defensive partnership of Rio Ferdinand and Nemanja Vidic meant his route to regular first-team action was blocked," United said.

Pique was a part of Man United's Premier League and Champions League winning teams this season.

"They are experiences I hope to repeat in the jersey of Barcelona," Pique said.

Pique is new coach Pep Guardiola's second offseason signing in two days.

On Monday, Barcelona paid Sevilla 14 million (US$22.1 million) for Seydou Keita, with the Mali midfielder agreeing to a four-year deal.

Barcelona is also interested in signing Uruguay under-21 defender Martin Caceres.

"We had received an offer from Barcelona, but it wasn't to Villarreal's complete liking and we have told Barcelona so," Villarreal president Fernando Roig told Efe on Tuesday. "If we cannot reach a deal, the player is Villarreal's."

The 21-year-old Caceres has also attracted attention from Spanish champion Real Madrid after his first season in Spain, spent on-loan at Recreativo Huelva.

Guardiola moved from reserve-team coach to replace Frank Rijkaard after Barcelona's second straight season without a trophy.

Barcelona's third-place finish was its worst in five years and it was knocked out in the Champions League semifinals by eventual winner Manchester United, though Pique did not feature in the two-legged series.

Defensive midfielder Edmilson left for Villarreal on Friday to begin what is expected to be an exodus of players, likely to include Ronaldinho, Deco and Samuel Eto'o, all of whom were key players when Barcelona won the 2006 Champions League.

AC Milan has expressed interest in signing Ronaldinho, Eto'o and fullback Gianluca Zambrotta.