Pablo Iglesias, the leader of Unidas Podemos, intends to resume talks "from the point where they had been stopped in July", El Pais newspaper said.
The document was already in the hands of Socialist leader Pedro Sanchez, but a response had not yet been received, the media outlet noted. The proposal reportedly consists of 10 measures based on the budget agreement that the parties reached last October. Moreover, Unidas Podemos offered four ways to integrate coalition members into the government.
In July, the Spanish parliament's lower house failed to approve the candidacy of Sanchez, whose party won the majority of seats in the snap elections in April. The main reason was due to the inability of PSOE to form a coalition with their fellow leftists from Podemos.
Since Sanchez did not secure the premiership, Spanish lawmakers now have until 23 September to resolve the political deadlock, otherwise the country will be forced to have its fourth national election in five years.
Sanchez replaced then-Prime Minister Mariano Rajoy last year after the latter was ousted by a no-confidence vote, which was prompted by embezzlement and money laundering scandals that had rocked his People's Party.