MADRID (Reuters) - The leader of Spain's anti-austerity Unidos Podemos party suggested on Tuesday it would not insist on an independence referendum in Catalonia as a condition for forming a national government with rivals after Sunday's election re-run.

The plebiscite on secession for Spain's northeastern region, favored by Podemos but rejected by all other large parties, had been a central dealbreaker in efforts to form a coalition after Spain's inconclusive election last December.

That parliamentary vote left Spain with a political landscape fragmented among four parties with none holding a large enough majority to establish a government.

Exhaustive talks in the following months failed to produce a majority coalition, prompting a re-run of the election on Sunday.

"Our proposal is that there is a referendum, but we are available to talk about anything. We wish to talk without red lines and hear other kinds of proposals," Unidos Podemos (Together We Can) leader Pablo Iglesias said in a radio interview.

Catalonia, a wealthy and populous region with its own language, has long had a strong independence movement, and even many residents there who do not support a split from Spain favor having their say on its future.

Unidos Podemos, an alliance formed last month between Podemos and far-left party Izquierda Unida, opposes a split of Catalonia from Spain. But its stance on the referendum has helped it build a strong power base in the region.

The leftist alliance is running second in national polls ahead of Sunday's vote and some surveys have shown a coalition with the Socialists could win a majority. [L8N19B0CL]

Socialist party leader Pedro Sanchez on Tuesday reiterated his opposition to a coalition with Iglesias, saying he would not back any proposal that could lead to the break-up of Spain.

(Reporting by Paul Day; Editing by Sarah White/Mark Heinrich)