The 24-year-old Argentinian has been on trial at Elland Road and impressed in the friendly games against Shelbourne and Barnet.

Becchio, who has also played for Real Mallorca, netted 28 goals in 50 appearances for Merida last term but turned down a new deal in Spain to seek a move elsewhere.

United manager Gary McAllister said: "We had had reports on Luciano, seen DVDs, and had a good look at him in training. We were very keen to get him in and he will be a real threat for us.

"I have been pleased with what I have seen of him in the games and, although he is lacking in match fitness, he realises that and we still have 10 days before the season starts. He is working hard."

Becchio started his career with Bocca Juniors before moving to Spain where he played at Barcelona and Mallorca before joining Merida.

Sheffield United have completed the capture of Wigan's David Cotterill alongside fellow new signings Matthew Spring and Justin Haber.

Blades manager Kevin Blackwell had put Cotterill, on loan at Bramall Lane for three months last season, at the top of his summer shopping list and he has now signed a three-year deal for an undisclosed fee.

The Wales international, who can play up front or on the wing, struggled to establish himself at the JJB Stadium but looks set to be a key player at Bramall Lane.

Blackwell said: "He is only 20 and a full international. He has shown glimpses of the real potential that enabled Bristol City to sell him (to Wigan) for £2m.

"David had set his heart on a move here, is prepared to look for a house in the area and we are showing the same commitment to bring him in."

Luton midfielder Spring has teamed back up with Blackwell for a third time after playing under the Blades manager at Leeds United and Luton Town.

The 28-year-old has signed a year-long loan deal, while Malta international goalkeeper Haber has agreed a two-year deal.

Doncaster have confirmed the permanent signing of Manchester City defender Matthew Mills, while key duo James Coppinger and James O'Connor have signed new deals.

Centre-back Mills has signed a three-year deal at Keepmoat Stadium, and joins for a club-record fee of £300,000.

Mills spent the majority of last season on loan at Rovers as they gained promotion to the Championship. Coppinger and full-back O'Connor have signed extensions until 2011.