Marine Le Pen's far-right party was poised Monday to strike an alliance with that of Hungarian Prime Minister Viktor Orban in the EU parliament, a day after being dealt a surprise defeat in French elections.

Officials from Le Pen's National Rally (RN) announced a "constitutive meeting of the new group, Patriots for Europe," which Orban launched just over a week ago, to be followed by a news conference in Brussels later Monday.

Orban's spokesman Zoltan Kovacs said on X, formerly Twitter, that "Patriots for Europe continues to grow as Marine Le Pen's National Rally joins".

With the RN, the new grouping stands to become the third-biggest force in the European Parliament, behind the conservative European People's Party (EPP) of European Commission President Ursula von der Leyen, and the Socialists & Democrats.

The announcement came a day after French voters relegated the anti-immigrant National Rally to third spot in legislative elections, despite surveys and a first-round vote suggesting it was on track to come first.

France's left-wing New Popular Front came top, but with insufficient numbers to form a legislative majority.

RN party chief Jordan Bardella, a lawmaker in the EU parliament, said late Sunday after the French result: "In the European Parliament from tomorrow (Monday) our MEPs will play fully their role in a big group that will weigh on the balance of power in Europe."

The RN -- which would be the biggest component of the Patriots of Europe grouping, with 30 lawmakers -- has also had past financial and ideological ties with Russia, to which Orban remains defiantly friendly.

Far-right parties did well in several countries in EU parliament elections a month ago, with the RN trouncing French President Emmanuel Macron's centrist camp by such a margin he felt compelled to call a snap election.

But in the EU legislature, the far-right remains splintered.

Up to now, the biggest faction was the European Conservatives and Reformists, dominated by the Brothers of Italy party of Prime Minister Georgia Meloni, who has toned down her previous euroscepticism in power.

The other main grouping was the Identity and Democracy party, which the RN held sway over and which took a more anti-EU stance.

Hungary's Fidesz, which left the EPP in 2021 just before it was about to be kicked out, had been seeking alliances to promote its nationalist and populist policies.

On June 30, Orban announced the launch of his Patriots of Europe vehicle to build such a grouping.

Austria's far-right Freedom Party (FPOe) and the centrist ANO of former Czech prime minister Andrej Babis signed up immediately.

Five other parties -- the Party for Freedom (PVV) of Dutch anti-Islam firebrand Geert Wilders, Portugal's far-right Chega party, Spain's Vox, the Danish People's Party and the Flemish nationalist pro-independence Vlaams Belang -- subsequently joined.

Matteo Salvini, who heads Italy's League, signalled Monday on X it too was preparing to join, hailing the formation of the Patriots of Europe as "determinant to change the future of this Europe".