The National Rally (RN) came out on top in the first round of voting on Sunday with 33 percent of the vote, raising the prospect that they might take control of government.
That has left the centrist camp of President Emmanuel Macron and a left-wing alliance scrambling to stop such an outcome.
"Obviously I was disappointed to see the direction our country is taking with a big level of support for a party that is against our values of unity and respect, and that wants to divide the French people," Kounde, the 25-year-old Barcelona defender, said.
"But there is a second round to come, nothing is decided yet, and I think it will be important to block the far right and the National Rally," he added after France beat Belgium 1-0 in Duesseldorf to reach the Euro 2024 quarter-finals.
"They will not lead our country to more liberty and unity. That is my position."
Kounde, who had already expressed such a view on social media ahead of the first round, is one of several France players to have spoken out against the far-right during the tournament in Germany.
Marcus Thuram called ahead of the elections for people "to fight to stop the RN winning".
Captain Kylian Mbappe and Aurelien Tchouameni also positioned themselves against "extremes".
