Jose Luis Rodriguez Zapatero, Spain's prime minister, and Artur Mas, leader of Catalonia's centre-right CiU party, reached a "global accord" on an autonomy statute for the wealthy region after a six-hour meeting at the Moncloa Palace - the prime minister's official residence - that ended late on Saturday.
Pasqual Maragall, Catalan's regional premier, said he expected a definitive agreement this week.
But left-wing nationalist party Esquerra Republicana de Catalunya (ERC) complained that the agreement with CiU did not cover all the parties.
Joan Ridao, ERC's spokesman in the Catalan parliament, said: "We think this is a premature agreement. Everything is still on the table and there is still a way to go."
A government spokesman said Zapatero would meet Josep Lluis Carod-Rovira, the ERC's leader, later on Sunday and also Joan Saura of ICV, the Catalan green party.
Spain's ruling Socialist party met on Saturday to discuss the statute and Zapatero called for one last effort to settle an issue which has caused political divisions and rumblings of discontent in the Spanish military.
Jose Montilla, the industry minister who is also a senior official in the Catalan Socialist Party, welcomed the deal with CiU.
"We think this is a premature agreement. Everything is still on the table and there is still a way to go"
"This means we can have a [Catalan] statute supported by a broad majority - a statute that Catalonia needs and that is good for Spain."
Catalonia wants the new autonomy statute - the first since 1979 - to recognise it as a nation within Spain, extend its fiscal and judicial powers and make it compulsory for public officials to speak Catalan.
The proposals have enraged right-wingers, who see them as a threat to Spanish unity.
The government fired Lieutenant-General Jose Mena Aguado, head of land forces, this month for saying the armed forces would have a duty to intervene if the Catalan statute was approved without changes.
The Catalan parliament overwhelmingly approved the text and sent it to Madrid last September.
Since then, the ruling Socialists have been negotiating with the Catalan parties to water down some of the provisions to make them more acceptable to Spaniards outside Catalonia.
Carod-Rovira, ERC leader, (above)
is to meet Zapatero on Sunday
No details of the agreement were yet available but Mas was expected to hold a news conference in Barcelona later on Sunday.
The CiU, is not part of the coalition that governs Catalonia, which is formed by the Catalan wing of the Socialist Party (PSC), the left-wing ERC and ICV, the Catalan greens.
But CiU has 10 seats in the Madrid parliament, the most of any independent Catalan party, and its support could be crucial when it comes to getting the new statute approved.
Negotiations have been held up by disagreement over Catalonia's financing and the use of the word "nation", which has angered Spain's conservative opposition and raised questions over whether the statute would violate Spain's constitution.
Newspapers reported that the term "nation" would appear only in the preamble of the statute, and would be used not in its legal sense but merely to denote the feeling of "nationality", the term expected to appear in the text, among Catalans.
Zapatero, a proponent of devolved government, is committed to revising Catalonia's statute.
But the proposal is almost certain to be strongly opposed by the conservative Popular Party which sees the extension of autonomy in Catalonia as the thin end of a wedge that could break up the Spanish state.