Serena Williams guaranteed her on-going status as the World No. 1 and moved to within one win of an all-time record sixth Sony Ericsson Open title with a 6-4, 3-6, 6-3 victory over elder sister Venus on Thursday evening in Miami.

The 27-year-old Serena broke in the fourth game of the first set to open up a 4-1 lead in her 20th meeting with her sister. With Serena serving for a one-set lead, Venus broke back for 5-4, but immediately surrendered her serve again as Serena closed out the set 6-4.

Breaks were exchanged early in the second set before Venus claimed the decisive break to lead 3-2 before going on to level the match as she broke Serena’s serve once more in the ninth game.

Breaks were exchanged early once again in the deciding set before Serena broke for a second time to take a commanding lead. With Venus serving at 3-5, a rifling backhand pass up the line earned Serena her first match point and she converted immediately as Venus netted a backhand after one hour and 55 minutes to level the head-to-head standing with her sister at 10-10.

"Venus never gives up," said Serena. "She gets a lot of balls back and has a massive serve. Just when you get her down she gets an extra umph and plays extra hard.  You can't lose focus at all, especially when you're up.  You have to actually play better when you're in the lead."

"It was a well fought match," said Venus. "I definitely would have liked to get a few more points off my serve. I think my serve wasn't going as well as I wanted today. But she brought a lot have balls back and played tough. I did the best I could today. I'm just looking to do better always."

Victory for Serena maintains her hold on the No. 1 spot in the Sony Ericsson WTA Tour Rankings. Had she lost prior to the final, she would have relinquished the top ranking to Russian rival Dinara Safina (l. to Stosur in third round) – whom she defeated to win her 10th Grand Slam singles championship at the Australian Open to initially reclaim the No. 1 ranking.

"I'm excited because I was thinking that I would love to remain No. 1, so obviously I was really excited about that," said Serena. "I mean, I think I was more happy about that than winning the match at the end."

Serena is chasing an all-time record sixth Sony Ericsson Open title and will make her seventh appearance in the final. After finishing runner-up to Venus in the 1999 final, she won three successive titles in 2002 (d. Capriati), 2003 (d. Capriati) and 2004 (d. Dementieva). She reclaimed the title in 2007 with victory over Justine Henin and last year defeated Jelena Jankovic to equal Steffi Graf’s record of five titles. She has a sparkling 52-5 event record.

The American is bidding for her second WTA Tour singles title of the season and the 34th of her career. Last season she won four titles, including victory at the US Open (d. Jankovic).

In the final, she will face Belarusian 11th seed Victoria Azarenka – who reached her first Premier final with a 6-3, 2-6, 7-5 victory over Svetlana Kuznetsova earlier in the day. In their last meeting in the fourth round of the Australian Open, Azarenka led 6-3, 2-4 before retiring due to dizziness and illness. Williams also won their first meeting in the third round of the 2008 Australian Open.

"She's playing well," said Williams of Azarenka. "She played me well and really, really tough in Australia. I mean, she was not feeling great, but I thought she did a pretty good job. I didn't serve well. I just remember I didn't serve well that day at all. Hopefully I can serve a little better."

World No. 6 Venus Williams had been chasing a fourth appearance in the Sony Ericsson Open final after capturing the title three times previously in 1998 (d. Kournikova), 1999 and 2001 (d. Capriati). She dropped to a 42-8 tournament record.

The 28 year old rebounded from a surprise second-round exit at the Australian Open (l. to Suarez Navarro) to become the only active player to win 40 WTA Tour singles titles when she triumphed in Dubai (d. Razzano). She later followed with her second title of the season on clay at Acapulco (d. Pennetta).