Ivanovic vows to regain form

Former world number one Ana Ivanovic is determined to get back to her best after winning just three games in her fourth-round clash with defending champion Kim Clijsters at the US Open.

Clijsters won 6-2 6-1 on Sunday to extend her winning streak at Flushing Meadows to 18 matches, the 27-year-old having won the title in 2005 and then coming out of retirement last year to lift the trophy again in only her 14th match and third tournament since returning to action.