LONDON - VENUS and Serena Williams' stranglehold on Wimbledon is poised to tighten even further on Thursday as the United States takes on Russia in this corner of south-west London.

Five-time champion Venus faces top seed Dinara Safina in what will be her eighth All England Club semi-final in 10 years while Serena, a two-time winner, tackles Elena Dementieva.

History favours the sisters. They have already played each other in three finals while there has been a Williams sister in a Wimbledon final in seven of the last eight years.

World number one Safina is still searching for a first Grand Slam title after finishing runner-up in the 2008 and 2009 French Opens as well as the Australian Open this year.

Dementieva, a semi-finalist here in 2008, has been runner-up at the 2004 French and US Opens and, like Safina, is still missing a Grand Slam breakthrough title.

'Do I feel invincible? I'd like to say yes, but I really do work at it,' said Venus who is bidding for three Wimbledon titles in a row and hasn't lost a set since the third round in 2007. The 29-year-old saw off Poland's 11th seed Agniezska Radwanska 6-1, 6-2 to make the semi-finals.

Serena was equally brutal with a 6-2, 6-3 dimissal of highly-regarded Belarusian teenager Victoria Azarenka who had beaten the American in the final in Miami in April.

Serena, the reigning US Open and Australian Open champion, holds a 5-4 career record over Dementieva and insists she and her sister are reaping the rewards for talent and work.

Top seed Safina reached her first Wimbledon semi-final with a 6-7 (5/7), 6-4, 6-1 win over unseeded German teenager Sabine Lisicki and insisted she is not daunted by facing Venus whom she beat on clay in Rome in May.

Dementieva, meanwhile has a 4-5 career record against Serena. Their first match-up was here in the fourth round six years ago with Williams coasting to a straight sets win. -- AFP