More than 200 centrist and left-wing candidates pulled out of France's legislative election runoff by a Tuesday deadline, in a move President Emmanuel Macron hopes will block the far right from winning power.

France votes on Sunday in the final round of snap legislative polls Macron called seeking a "clarification" in politics after his camp was trounced in European elections last month.

His gamble backfired, with the far-right National Rally (RN) of Marine Le Pen winning the June 30 first round. But the key suspense now is whether the RN can get enough seats to form a government.

Faced with the prospect of the far right taking power for the first time since France's occupation by Nazi Germany during World War II, Macron's camp and the left have urged a broad "Republican Front" to stop Le Pen's anti-immigration and eurosceptic party.

By Tuesday evening's deadline to register, more than 210 pro-Macron or left-wing candidates had pulled out of contests in an attempt to prevent the RN winning seats, in what appeared a welcome development for the presidential camp.

But Le Pen appeared to row back on previous comments that the RN would only form a government with an absolute majority of 289 of the 577 seats in the National Assembly, saying it would still try if slightly below this figure.

She said her party would seek to form a government and make her 28-year-old protege Jordan Bardella prime minister even with as little as "for example, 270 deputies", requiring them to find support from another 19 MPs to govern.

"If we then have a majority, then yes, of course, we'll go and do what the voters elected us to do," she told broadcaster France Inter.

If Bardella becomes prime minister, this would create a tense period of "cohabitation" with Macron, who has vowed to serve out his term until 2027.

Prime Minister Gabriel Attal, 35, said late on Monday it "would be catastrophic for the French" to give the far right an absolute majority. (AFP)