Serena and Venus Williams delivered singles victories Sunday to lift the United States to a 3-2 Fed Cup playoff victory over Sweden that will keep America in the elite World Group.
Venus Williams persevered to deliver the clinching point, sealing a 6-3, 7-5 victory over Johanna Larsson on her eighth match point.
The seven-time Grand Slam champion had been rolling toward the win, serving for the match and the tie at 5-4 in the second set when she delivered three double faults to drop her serve.
She immediately broke back to take a 6-5 lead, but had to claw through a 12th game that went to deuce nine times.
"She started lifting her game, but thanks to all the support here I was able to give it to the US," said Williams, who had seven of her 11 double faults in the second set but hung on to give the United States an unbeatable 3-1 lead.
The Americans then opted out of the meaningless doubles, giving Sweden a walkover win and making the final score of the tie 3-2.
Venus was given singles duty at the last minute by US captain Mary Joe Fernandez, who apparently felt that 20-year-old Sloane Stephens hadn't bounced back adequately from her error-strewn 6-4, 4-6, 6-1 loss to Sofia Arvidsson in the opening match of the tie on Saturday.
World number one Serena Williams had put the Americans back on track Saturday with a win over Larsson, and she put the 17-time champion United States up 2-1 with a dominant 6-2, 6-1 win over Arvidsson on Sunday.
Serena fired 10 aces and broke Arvidsson twice in each set en route to the victory.
Serving to extend the first set, Arvidsson double-faulted to give Williams a break point, then netted a backhand to surrender the frame.
Williams was even more dominant in the second set, racing to a 5-0 lead before Arvidsson finally held serve.
Back-to-back aces gave Williams triple match point, which she converted with another service winner.
"Today I played better -- I had to going up against the number one player from Sweden who had a really good win over our star player in America," said Williams, who stretched her perfect Fed Cup singles record to 10-0.
"It was important for me to take this match really serious."
The tie saw Serena and her former top-ranked sister Venus playing Fed Cup together for the first time in 14 months, and with the win, the United States avoided relegation to World Group II after losing their 2013 first-round tie 3-2 to Italy in February.