Venus Williams survived her first match in six months to help the United States beat Belarus and reach the play-offs for promotion to the Fed Cup World Group.

Leading 2-0 overnight, Serena Williams had to work hard in beating Anastasia Yakimova 5-7 6-1 6-1 in Sunday's first singles match in Massachusetts to give the Americans an unassailable 3-0 lead.

After Christina McHale beat Kustova, on came seven-time Grand Slam champion Venus alongside Liezel Huber to cruise past Yakimova and Daria Kustova 6-1 6-2 to secure the team a 5-0 victory.

Venus had not played since pulling out of the US Open in August when she revealed she had been diagnosed with the auto-immune disorder Sjogren Syndrome.

The relieved 31-year-old said: "It was perfect conditions. I'm not sure what my plans are. For me it's kind of week-by-week and just see what happens. I try not to put pressure on myself.

"I'm still fighting fatigue. I'm getting better. I mean, it just takes a while to kind of find the right medicines that work, to get stronger.

"Once you do have a chance to get on the court, it takes at least six weeks to build a nice baseline so you just don't get hurt.

The big push for me is the Olympics this year, so I can get back on the court and get my ranking up.

"If I'm healthy, I'm not worried about my ranking. It's just about my body co-operating. It's about being able to play matches in a row. Right now I'm not sure how much I can do with that, but we'll see."

USA now progress to the World Group I play-offs in April. Belarus, missing Victoria Azarenka due to injury, will compete in the World Group II play-offs.