Ngolo Kante's goal eight minutes into the second half secured a 1-0 for France away at Portugal and sent the world champions into the finals of UEFA's Nations League and could also ultimately decide which of the two finishes top of their group.
The pair were level on 10 points coming into the clash at Estadio da Luz in Lisbon, but the Chelsea man's strike gives Les Bleus a three-point cushion heading into their final fixture at home to Sweden.
Coach Didier Deschamps opted to go without Olivier Giroud in attack and favored Anthony Martial instead and was nearly rewarded when the Manchester United man hit the crossbar with a header after Kingsley Coman, Martial and Adrien Rabiot all had chances.
Portugal had limited chances in the first 45, creating seven shots but did go close through Danilo Pereira after he beat Rabiot in the air, but the hosts were grateful to goalkeeper Rui Patricio for a string of excellent saves -- notably to deny Martial twice -- as they continued to struggle against their bogey side.
Despite a bright open to the second half, the Portuguese fell behind to Kante's crucial strike after Patricio could only parry Rabiot's effort following a one-two with Antoine Griezmann into the path of the onrushing midfielder.
Portugal responded and went close through Jose Fonte -- who plies his trade in France with Lille OSC -- but his late header hit the post.
Down the other end, Patricio continued to frustrate Martial, and denied the former Monaco and Lyon man after Lucas Hernandez had teed him up after Griezmann created the opening.
France captain Hugo Lloris came up big as time ticked away, denying Joao Moutinho's excellent effort with an even better save and Presnel Kimpembe also made sure that Cristiano Ronaldo was not allowed a headed effort at goal.
Lively substitute Trincao might have had a penalty late on but he refused to go down after a possible obstruction and the chance passed.
It finished 1-0 to France and Deschamps' men now have the chance to be the first team ever to win the World Cup, Euros, Confederations Cup and Nations League.