Great Britain were unable to reach their first Billie Jean King Cup final since 1981 as a surprise run came to an emotional end against Australia.

Britain trailed 1-0 when Heather Watson lost to Storm Sanders in the singles.

Harriet Dart levelled by beating Ajla Tomljanovic - but Australia progressed.

Australia, seven-time champions and ranked as the world's best nation, will play Switzerland or the Czech Republic in Sunday's final after Sam Stosur and Sanders won 7-6 (7-1) 6-7 (5-7) 10-6 against Barnett and Nicholls.

"To come that close, it hurts. It's as simple as that," Great Britain captain Anne Keothavong said.

While Barnett and Nicholls welled up and were consoled by Dart in the moments following their defeat, the initial upset will quickly be replaced by pride after what has been an encouraging week for the British team.

Few expected them to go as far as they did, especially with the absence of Emma Raducanu through injury.

But they continually upset the odds and the rapturous standing ovation they received at the end of their semi-final defeat was a measure of the connection they had formed with the home fans.

Barnett, 29, and Nicholls, 28, only made their debuts for Great Britain this week and, backed by a partisan home crowd, pushed their experienced opponents all the way.

They have enjoyed the best season of their careers, climbing to the cusp of the world's top 50 after winning their first WTA title in August in Canada.

Victories in the doubles rubbers against Kazakhstan and Spain in the BJK Cup Finals announced their arrival on an even bigger stage and it was an indication of how far they have come in a short space that they were close to beating Stosur and Sanders.

The pair oozed confidence and had they taken a set point at 6-5 to win the opener, the outcome might have been very different.

Former doubles world number one Stosur and Sanders, a semi-finalist at this year's US Open, showed their pedigree to race away with the tie-break and stopped the Britons from serving out the second set at 5-4.

Barnett and Nicholls maintained composure to fight back from 5-4 in the second tie-break, forcing a match tie-break, which was a first-to-10-points contest.

The British pair recovered from 6-3 down to 6-6, only for Stosur and Sanders to win the final four points and leave Britain deflated.

"I'm gutted for everyone right now, but also I think we have to try and keep things in perspective," added Keothavong.

"I don't know how many people gave us much of a chance really to even come through the group stages.

"It really is a fantastic achievement to reach the semi-finals, but we felt we could have gone further. That's why it hurts so much."

Dart epitomises British spirit

Great Britain have been the underdogs throughout the competition but one thing we have learned about Keothavong's side this week is to not write them off.

Having being handed a spot as the host nation, they were put into a difficult group with Spain and Kazakhstan, who are both ranked higher.

They had also suffered another a blow before the 12-team finals started when Raducanu - the 2021 US Open champion and Britain's highest-ranked player - was ruled out with a wrist injury.

After losing to Kazakhstan on Tuesday, they could have been eliminated before even playing Spain on Thursday.

But Spain, led by former world number two Paula Badosa, won 3-0 against Kazakhstan in their opening group match, meaning Great Britain then needed to beat the Spanish 3-0 - which they did in a stunning performance that Keothavong described as "something really special".

Dart was instrumental in that success.

Stepping up in Raducanu's absence, she produced one of the performances of her life to outplay Badosa and create another memorable moment in what has been the best year of her career.

And on Saturday, the 26-year-old - who has broken into the world's top 100 for the first time this year - did the same against 33rd-ranked Tomljanovic.

"Harriet has been a great example to everyone this week. I do think sometimes she doesn't get the credit she deserves," Keothavong said.

"For her, it's now about producing it on a week-in, week-out basis."

Watson not as fresh in early start

Dart knew she had to win to keep alive British hopes after 30-year-old Watson lost 6-4 7-6 (7-3) to Australia's Sanders.

Great Britain had played their previous two ties in the evening and the change to a morning start on Saturday seemed to affect Watson.

"I think I just didn't feel as fresh as I did then," she said. "It's very different playing at 10am when we have been having late starts.

"I don't feel like I played as well as I did in the first match [against Spain], I felt a bit heavier today, missed a lot more first serves.

Watson was brilliant in Thursday's must-win group tie against five-time champions Spain as the hosts reached the last four, but could not reach the same level against an opponent ranked 104 places below her.