Roger Federer suspects he knows why he hasn't been able to add to his record 16 Grand Slam titles the last two years.

The Swiss great last won a major championship at the 2010 Australian Open. He insists this has nothing to do with a declining game but "a bit of confidence not on my side and on my opponent's side."

"I've had some tough losses over the past couple of years," Federer said, without referring to any specific matches.

Federer is ranked No. 3 and is joined in the field by No. 1 Novak Djokovic and No. 4 Andy Murray for the Dubai Championships, which start Monday.

Having broken Pete Sampras' mark of 14 Grand Slam singles titles, Federer missed breaking the American's 286-week reign at No. 1 by a single week.

"It would be great having that record but my life is very much OK without it, too," Federer said. "Pete is a good friend and was an amazing champion for our game. I don't need to break every record he has. I came so close and I could have chased it if I had wanted to. I didn't choose to."

Federer still believes he can return to No. 1, however, noting that he has won three titles in the past four months — the most recent in Rotterdam this month.

"I feel if I play really well until the U.S. Open, then obviously there is a shot. But then again there is a shot for about 10 players," Federer said. "I am aware I'm not the only one. But I feel like I'm on a good run right now. I've won a lot of tournaments in a short time, which gives me a lot of confidence."