"I'm not here on holiday, I'm here to win and score a lot of goals," said the 31-year-old forward who made his debut at home to the San Jose Earthquakes on Saturday.
"I'm excited about the opportunity," Keane told reporters. "I'm looking forward to hopefully bringing a lot of success."
"As a player you always have expectations and pressure on you. I've had that since I was 17," said Keane who also had spells with Liverpool, Inter Milan, Celtic, Wolverhampton Wanderers, West Ham United, Leeds United and Coventry City.
"It's up to me to accomplish [my targets] and I think I can do it. I played in the Premier League for a long time and I did what I had to do - I felt it was time for a new challenge."
"Our job just got easier by bringing Robbie here," Donovan said. "He looked good, looked sharp and I think he's going to fit in well with this team."
Former England captain Beckham said: "We know he's going to score goals. He's scored goals everywhere he's been."
