Serbia's tennis star Ana Ivanovic has hired Heinz Gunthardt, formerly Steffi Graf's coach, released by the former world number one on her website on Monday.

Gunthardt, who helped Graf win 12 Grand Slam titles, "will accompany Ana to the BNP Paribas Showdown in New York next week, thus marking the pair's first event together", Ivanovic said on her website.

"The appointment of Gunthardt ends, or at least suspends, Ana's active participation in the Adidas Player Development Programme: the 22-year-old was formerly working with Sven Groeneveld on a part-time basis", the Serbian said in the statement.

After a series of losses in 2009, Ivanovic has fallen to number 23 in the WTA rankings and was knocked out in the second round of the Australian Open in January.

In 2008, Ivanovic was briefly world number one, after winning the French Open.