French President Emmanuel Macron announced Thursday that he will seek a second term in office at elections next month, with Russia's war in Ukraine likely to eclipse the campaign but boost his chances.

Macron formally announced his attempt to become the first French president to be re-elected in 20 years in a letter to the French people published online by numerous news sites.

There was little suspense about the 44-year-old's intentions, but the announcement has been repeatedly delayed because of the crisis in eastern Europe that has seen Macron take a prominent role in diplomatic talks.

"I'm a candidate to invent, with you, and faced with the challenges of this century, a singular French and European response," he said.

"I am a candidate to defend our values that are threatened by the disruptions of the world," he added.

Macron acknowledged that the election would not be a normal one due to Russia's war on Ukraine.

"Of course, I will not be able to campaign as I would have liked because of the context," he said, while vowing to "explain our project with clarity and commitment".

Ahead of Friday's deadline for candidates to stand, polls widely show him as the frontrunner in the two-round election on April 10 and 24, with the war focusing attention on foreign policy rather than the domestic issues favoured by his opponents.

"In a crisis, citizens always get behind the flag and line up behind the head of state," said Antoine Bristielle, a public opinion expert at the Jean-Jaures Foundation, a Paris think-tank.

"The other candidates are inaudible. In every media, all anyone is talking about is the invasion," he told AFP.

One ruling party MP told AFP this week the Ukraine crisis meant that Macron's rivals were "boxing on their own", while several polls have shown his personal ratings rising.

The former investment banker admitted in a national address on Wednesday night that the crisis had "hit our democratic life and the election campaign" but promised "an important democratic debate for the country" would take place.

Voter surveys currently tip the centrist to win the first round of the election with 26 percent and then triumph in the April 24 run-off irrespective of his opponent.

 Rivals

After five tumultuous years in office, Macron's biggest challenge comes from opponents on his right who accuse him of being lax on immigration, soft on crime and slow to defend French culture.

These include the conservative Valerie Pecresse from the Republicans party, far-right candidate Marine Le Pen and anti-Islam media pundit Eric Zemmour.

On the left, four mainstream candidates are competing, which is expected to split the vote and lead to all of them being eliminated in the first round.

Socialist Party candidate Anne Hidalgo said the announcement was "not a surprise."

"The democratic debate, of one programme versus another that I have been calling for for months, can finally take place," she said in a statement.

Macron's camp have been looking for the right moment to launch his candidacy since early February, but the Ukraine crisis has seen his agenda filled with either foreign trips or talks with other leaders.

He spoke for the third time in a week to Russian President Vladimir Putin on Thursday and again with Ukrainian counterpart President Volodymyr Zelensky.

Striking a note of humility, Macron added in his letter that "we have not got everything right".

"There are choices that after the experience I gained with you I would have no doubt made differently," he said.

A recent poll by the Elabe group, published March 1, showed that confidence in Macron's "ability to tackle the main problems of the country" was up a massive five points in a month.

Another by the Harris Interactive group showed 58 percent of French people held a favourable view of his handling of the Ukraine crisis

Allies of the president are quietly confident, but analysts warn many voters remain undecided and that sentiment can swing sharply in the final weeks of campaigning.