MADRID (Reuters) - Catalonia’s new secessionist leader, Carles Puigdemont, said his regional government will not make a unilateral declaration of independence from Spain, acknowledging that sufficient public support for a break with Madrid was still lacking.

New Catalan President Carles Puigdemont (C) receives a medal from outgoing Catalan President Artur Mas during Puigdemont's swearing-in ceremony as President of the Generalitat de Catalunya at Palau de la Generalitat in Barcelona, Spain, January 12, 2016. REUTERS/Albert Gea

Puigdemont took office as regional president on Tuesday as head of the nationalist coalition Junts pel Si (Together for Yes), ending months of in-fighting among separatist factions.

The move gave renewed vigour to the push for the northeastern region, Spain’s wealthiest, to secede. The campaign is fiercely opposed by the main national political parties.

Separatist leaders have previously spoken of an 18-month time-frame and a unilateral declaration of independence.

But Puigdemont appeared to acknowledge in an interview with Catalan station TV3 that this was unrealistic.

“Do we have sufficient strength to declare independence for Catalonia with this parliament? Still no,” Puigdemont told TV3 on Thursday night, in his first interview since taking office.

The results of a September regional election gave him a mandate to push forward with the independence campaign, he said. But the present situation was a period of “post-autonomy and pre-independence” transition.

Although the separatist coalition has the most seats in the regional parliament, opinion polls show that a majority of the 7.5 million people in Catalonia, which has its own language and culture, say they want to remain part of Spain but with greater autonomy on issues such as tax.

Before a Catalan republic could be declared, Catalans must endorse a new constitution in a referendum, Puigdemont said. He also appeared to be flexible over the 18-month time frame, saying the process must first be legally secure.

The developments in Catalonia take place in a fraught national political scene in which Spain is without a government following an inconclusive election last month.

The conservative People’s Party won most seats but lost its outright majority in parliament. Unless a coalition can be formed, the country is likely to go to the polls again.

The PP, the Socialists and the centrist Cuiadadanos all oppose a referendum in Catalonia, although the left-wing Podemos supports the idea of allowing it.

Puigdemont caused a stir when he took office in a ceremony on Tuesday without swearing allegiance to the Spanish king or the constitution.