Unseeded American Jamea Jackson beat defending champion Maria Sharapova [ Images ] 6-4, 6-4 on Saturday to become a surprise finalist at the Birmingham Classic tennis.

Jackson's victory ended the Russian's bid for a third straight title at the Wimbledon [ Images ] warm-up event and was her first win over the 2004 Wimbledon champion after two previous defeats.

In Sunday's final, the 81st-ranked Jackson will face Russian Vera Zvonareva [ Images ], who defeated Meilen Tu of the United States 5-7, 6-4, 6-3 in the other semi-final.

Until she injured her ankle in practice at the end of April, Sharapova had enjoyed an impressive year, reaching the semi-finals at the Australian Open [ Images ], winning the title in Indian Wells and then reaching the final in Miami [ Images ].

Last week, the 19-year-old Sharapova lost to compatriot Dinara Safina [ Images ] in the fourth round of the French Open [ Images ].

Sharapova will hope to come back to form during Wimbledon fortnight which starts on June 26.