France and Switzerland both moved to within one point of the Davis Cup final on Friday when they swept the opening two singles rubbers in their respective semi-finals.
In Geneva, Roger Federer and Stan Wawrinka both won to put Switzerland 2-0 up against Italy.
In Paris, Richard Gasquet and Jo-Wilfried Tsonga were the winners against defending champions the Czech Republic.
Both countries now just need a win in Saturday's doubles to be sure of reaching the November 21-23 final.
Federer defeated Simone Bolleli 7-6 (7/5), 6-4, 6-4 in the opening rubber of their semi-final against Italy and then Wawrinka crushed Fabio Fognini 6-2, 6-3, 6-2.
That left the Swiss on the cusp of reaching the Davis Cup final for just the second time after finishing second to the United States in 1992.
Federer, a 17-time Grand Slam champion who has never appeared in a Davis Cup final, was taken all the way in the first set against Bolleli, but eased ahead by winning the tie-break.
But once Federer grabbed the first service break of the match after more than an hour's play to move 5-3 up, Bolleli's standard of play started to fall away.
Another break of serve thanks to a netcord in the third game of the third set sent Federer on his way and he made no mistake after that.
"It was quite frustrating at times but that's indoor tennis," the Swiss star said of a match played in front of a capacity 18,000 crowd.
"Playing beautiful, nice points didn't really matter. I just stayed with him."
Australian Open champion Wawrinka was never troubled by Fognini, dominating the Italian with 37 winners, and 16 aces.
Playing at the French Open base of Roland Garros in Paris, French number one Tsonga coasted to a 6-2, 6-2, 6-3 win over Lukas Rosol following Gasquet's upset 6-2, 6-3, 6-2 victory over top Czech player Tomas Berdych.
"I am very proud of the way they played today," French captain Arnaud Clement said of his players.
"For Richard it was perhaps the best match he has played in the Davis Cup and he chose right moment to do it.
"Bravo to both of them and we are well-placed this evening, but we still have a long way to go."
Tsonga won five games in a row from 2-2 in the first set to pull clear of Rosol, who was chosen ahead of veteran campaigner Radek Stepanek.
He stayed in total control of the match in the second set despite some big-hitting from Rosol and, when he broke again in the fourth game of the third set, there was no way back for the outgunned Czech.
"All merit goes to Richard who gave me the perfect platform. He played an extraordinary match and that helped me to win mine.
"But they won't give in as easy as that so we have to stay focussed and play a great match."
The Czechs are seeking a third straight Davis Cup title, while France are aiming for a first win in the annual team competition since 2001.
Gasquet, who was chosen ahead of recent US Open semi-finalist Gael Monfils, took control early on against Berdych in front of a packed Philippe Chatrier centre-court and he pocketed the first set 6-3 with a superb backhand drive down the line.
And it was the power of the Gasquet backhand again that led to the world number six Czech dropping serve twice in a row at the start of the second set.
The Czech team spearhead claimed one of those breaks back to get to 3-1 but Gasquet held firm and broke again to take the set 6-2.
Berdych held serve to open the third set but he was broken to love two games later as an on-fire Gasquet continued to dominate on the claycourt.
Gasquet had two match points in the ninth game and a double-fault from Berdych on the second of those gave the French a crucial opening point.
"I had a lot of pressure, but the crowd was unbelievable," said Gasquet.
"I didn't shut it out, I tried to hear it. The atmosphere is incredible. Court Philippe Chatrier is built for the Davis Cup."