French President Nicolas Sarkozy has ruled out doing any election deal with the far-right National Front but said its voters should not be demonised.
"There will be no agreement with the National Front, and no [National Front] ministers," he told France Info radio.
After losing the first round of the presidential election, he needs to win over far-right voters for the second.
Socialist rival Francois Hollande has argued that some National Front supporters belong on the left.
On Wednesday, he said he respected the wishes of centrist candidate Francois Bayrou, who has yet to declare whom he will back in the second round.
Mr Bayrou won 9.1% of the vote on Sunday, coming fifth, just behind the far left's Jean-Luc Melenchon on 11.1%.
The shock of election night for many was the 18.1% won by National Front candidate Marine Le Pen, putting her third behind Mr Sarkozy on 27.1% and Mr Hollande on 28.6%.
"We need to speak to the 18% who voted for Marine Le Pen," Mr Sarkozy said.
"I don't regard this 18% as people with extreme-right ideas... but I don't want ministers from the National Front. I've never wanted that."
Ms Le Pen is not expected to make her position clear until next week when she addresses a National Front rally on 1 May.
Speaking to France 2 TV, Mr Hollande said he would respect whatever Francois Bayrou would "say or do" for the second round, and that he did not want to put pressure on him.
Earlier, the Socialist candidate argued that part of the Le Pen electorate came from the left and "should be on the side of progress, equality, change, shared effort and justice".
"It is up to me to convince them that the left defends them," he said.