Substitute striker Natasha Kai scored an extra time winner to help defending champions the United states earn a laboured 2-1 victory over Canada to reach the semifinals at the Olympic women's soccer tournament?in Shanghai?on Friday.

The U.S. was held to a 1-1 draw with Canada after 90 regular minutes, whose first half suffered a 100-minute-long break due to the bad weather, making the marathon-like game ended after a total of four hours.

Kai netted in a nice diving header 12 minutes into the playoff following Shannon Boxx's left side center to end the Cannucks' hope.

The Americans will meet either Japan or hosts China in the semifinal on Aug. 18.

Angela Hucles put the Americans ahead in the 12th minute following Heather O'Reilly's head flicker from a Amy Rodriguez pass left Hucles facing an empty net at the far post.

Eight minutes later Swedish referee Jenny Palmqvist decided to suspend the match as a sudden thunderstorm hit the Shanghai Stadium. The heavy rain and fierce lightning made it not safe for players to continue playing.

The match began on 18:00(local time), broke on 18:20 and was resumed on 20:00 after BOCOG officers saw the rain reduce and the lightning disappear.

Canada seemed to restore their energy after the break. Ace striker christine Sinclair levelled with an outstanding long-range shot on 30 minutes to beat a full-stretched Hope Solo.

The lacklustre second period has witnessed both teams making too many mistakes in the passing and organization, and both sides did awfully in the finishing.

Amy Rodriguez nearly sealed victory for the Americans at the last minute of the regular time, only to find her low drive parried by a diving Karina LeBlang.

(Xinhua News Agency August 15,2008)