Thiem survived two tough sets against Marco Cecchinato before cruising through the third for a 7-5, 7-6, 6-1 success.

The second set proved particularly tough before the dominance of the seventh seed eventually told against a player who had stunned Serbia's Novak Djokovic in the quarter-finals.

"The big key was the second-set tie-break because it was very close and I saved I think three set points," said Thiem.

"If I lost that tie-break it would have been a very close match and I didn't want that.

"Of course it's very important to have a good recovery now. 

"I'll watch the other semi-final to study my opponent and then it's full power on Sunday (June 10)."

Nadal simply had too much power and consistency for Argentina's fifth seed Juan Martin del Potro in the match that followed.

The Spaniard required barely two hours to win 6-4, 6-1, 6-2.

"The first set was very difficult, there were lots of opportunities for Juan Martin del Potro and I was perhaps a little lucky to win it," Nadal said afterwards.

"I am very happy to be in another Roland Garros final, it is the most important tournament of my career."

He has lost just twice in 87 singles matches at the French Open.

Thiem will start as the underdog in his first major final, but the 24-year-old has beaten his 32-year-old opponent on clay.

This included a quarter-final success in Madrid last month.

Prevailing on Nadal's favourite court in Paris over five sets will be far harder, however.

Romania's Simona Halep will first play American Sloane Stephens in the women's singles final tomorrow.