Santana Lopes reshuffled his government last week

Mr Santana Lopes, who heads a centre-right coalition, made the announcement after meeting the president.

His four-month-old administration has faced strong criticism over allegations of media interference and a lack of co-ordination between ministers.

Former premier Jose Manuel Barroso left to head the European Commission.

President Sampaio said in a statement he would meet leaders of parties in parliament and the advisory Council of State to discuss the situation, Reuters news agency reported.

The meetings can be held over a few days and are part of the procedure to dissolve parliament and call an election. Elections had been scheduled for 2006.

Mr Santana Lopes said he disagreed with the president's decision as his coalition holds a majority in parliament.

Political infighting

Mr Sampaio seems to have decided that an internal government crisis was undermining political stability, says the BBC's Alison Roberts in Lisbon.

The row was sparked by the resignation of the government minister for youth and sport, Henrique Chaves, who accused the prime minister of dishonesty and disloyalty after a cabinet reshuffle.

A spokesman for Mr Sampaio said the president believed the prime minister lacked "the indispensable political conditions to continue to mobilise Portugal... in a coherent, rigorous and stable fashion".

Rival party leaders had called for elections in July when Mr Barroso moved on.

Instead, Mr Sampaio appointed Mr Santana Lopes, with the warning that he must maintain economic and political stability.