France's left-wing parties still plan to form a joint government after they emerged as the strongest bloc in parliament in a snap election, but any pact is unlikely to come this week, the head of the Socialist Party (PS) said on Monday.

"Nothing will happen before July 18." Olivier Faure told France 2 television, referring to the date the newly elected National Assembly is due to convene for the first time.

The New Popular Front (NPF), a hastily assembled alliance ranging from socialists and Greens to the communist party and the hard-left, eurosceptic Unbowed France (LFI), won the parliamentary election earlier this month but fell well short of a majority.

"We will take our time, don't worry," Faure said. His comments, coming after a week of fruitless talks within the bloc, marked a shift in tone.

Following their surprise election win on July 7, Faure and other leaders said they were prepared to form a government and would come up with a name for the prime minister's seat within days. However, no progress has been made since then.

President Emmanuel Macron last week urged the mainstream parties in France's hung parliament to form a coalition able to muster a "solid" majority, putting pressure on the more moderate parts of the NFP to ditch LFI and join Macron's centrists.

Even if the left manages to agree on a name to put forward as government chief, it was still unclear if Macron would accept to appoint a premier from its ranks as any such government would lack roughly 100 seats in parliament to form a stable majority.