Australia's Ashleigh Barty and Casey Dellacqua lost the US Open women's doubles final in three sets on Saturday to fifth-seeded Czechs Andrea Hlavackova and Lucie Hradecka.
Eighth-seeded Barty and Dellacqua took the first set on a tiebreak but eventually went down 6-7 (4-7) 6-1 6-4 in New York.
Dellacqua and Barty, in only their eighth event together, were also runners-up at this year's Australian Open and Wimbledon.
Barty, just 17, said there was no real secret to their successful partnership.
"It's just about coming out here and having some fun with a friend," she said.
"It's been amazing playing with Casey and I've been very lucky to have her on my team.
"Hopefully one day we'll have one of these trophies. We'll just knuckle down."
They are the first Aussie women's pair to reach the US Open final since Wendy Turnbull and Kerry Melville Reid in 1978.
It was a second grand slam title in as many days for Hlavackova, who won Friday's mixed doubles alongside Max Mirnyi of Belarus.
"It has been amazing," Hlavackova said. "I cannot believe I won two Grand Slams in two days. I want to thank Lucie. She helped me as much as Max did."
She became the first player to win two US Open titles since Zimbabwe's Cara Black in 2008, when she joined American Liezel Huber to win the women's doubles title and India's Leander Paes to win the mixed.
The first all-Czech duo to win the US Open crown took $US460,000 ($A506,580). They previously won the 2011 French Open title.
Dellacqua revealed that she was gay earlier in the tournament when she announced that she and her partner Amanda had become parents last month of a baby boy named Blake.
The 28-year-old said motherhood put Saturday's defeat into perspective.
"You get out here to do your best, to play for your family," she said. "I look forward to seeing them soon."
