PARIS: Andy and Jamie Murray kept Great Britain's hopes of retaining their Davis Cup title alive on Saturday while 2005 winners Croatia took a step closer to the final.
In Glasgow, the Murray brothers defeated Argentina's Juan Martin del Potro and Leonardo Mayer 6-1, 3-6, 6-4, 6-4 while in Zadar, Marin Cilic and Ivan Dodig downed top-ranked French pair Pierre-Hugues Herbert Nicolas Mahut 7-6 (8/6), 5-7, 7-6 (8/6), 6-3.
Both semi-finals are finely-poised with Argentina and Croatia holding 2-1 leads ahead of Sunday's reverse singles.
Leading 2-0 from Friday's singles, Argentina captain Daniel Orsanic selected Del Potro alongside Mayer instead of Federico Delbonis as he looked to kill off the semi-final.
However, the tactic backfired as world number two Andy Murray and his older brother Jamie secured a thrilling victory.
"Yesterday was a very tough day. To come out and get the win with Jamie today was great," three-time Grand Slam winner Andy said.
"He played unbelievably well throughout the whole match. We are 2-1 down and it is a tough position to be in, but it is a better position that we were in at the beginning of the day and I still believe we can come back."
Argentina are looking to reach their fourth final in 10 years.
Kyle Edmund is scheduled to face Del Potro on Sunday although the Argentine star hinted that he may sit out what could be the decisive rubber as Andy Murray is favourite to defeat Guido Pella in the first reverse singles.
After his five-hour and seven-minute 6-4, 5-7, 6-7 (5/7), 6-3, 6-4 epic win against Andy Murray on Friday, the expectation was that Del Potro, still working his way back into the game following wrist surgery, would take the day off on Saturday.
The gamble to pick the 27-year-old didn't look like paying off with the Argentine pairing initially looking like strangers on the court.
"I felt tired but that is normal. I think for the team it was the best option to play the doubles," said del Potro.
"I think we did really well. We had some chances but we couldn't win."
Cilic was a surprise call-up for the doubles for Croatia as he replaced Marin Draganja.
But he didn't let his side down as he secured his second point of the weekend when he and Dodig downed Herbert and Mahut to follow their win over Bob and Mike Bryan in the quarter-final success against the United States.
In Sunday's reverse singles, 2014 US Open champion Cilic faces Richard Gasquet while Borna Coric will tackle Lucas Pouille.
On Friday, Gasquet beat Coric 6-2, 7-6 (7/5), 6-1 before Cilic saw off Pouille 6-1, 7-6 (7/4), 2-6, 6-2.
In the play-offs, where the winners earn places in the World Group in 2017, Olympic champions Rafael Nadal and Marc Lopez beat Leander Paes and Saketh Myneni 4-6, 7-6 (7/2), 6-4, 6-4 to secure a 3-0 triumph for Spain over India in New Delhi.
In Sydney, John Peers and Sam Groth earned a 6-4, 6-2, 6-7 (3/7), 7-6 (7/2) win and an unassailable 3-0 advantage for Australia against Slovakia.
Belgium, last year's runners-up, also secured their World Group status thanks to a 3-0 victory over Brazil in Belgium. Japan made sure of their place in the elite section with a 3-0 victory over Ukraine in Osaka.
In other ties, Canada beat Chile 3-0, Switzerland led Uzbekistan 2-1, Russia were 1-0 to the good over Kazakhstan in a rain-hit tie while Germany carved out a 2-1 lead over Poland.