We are firmly convinced that the future of our country lies in a Europe that is stronger and knows how to speak with one voice

Silvio Berlusconi

Mr Ruggiero quit in a row over Italy's unenthusiastic adoption of the new euro currency, prompting expressions of concern about the situation from senior ministers in France, Germany and Belgium.

In a newspaper interview, Mr Berlusconi said that Italy did fully support a united and integrated Europe.

"We are firmly convinced that the future of our country lies in a Europe that is stronger and knows how to speak with one voice and knows how to follow up economic integration with political integration, with a new constitution," he told Corierre della Serra.

Renato Ruggiero was unhappy at the way Italy adopted the euro

Mr Berlusconi told the newspaper he expected to remain as both prime minister and foreign minister for some time.

"I intend to keep the interim [portfolio] for at least six months, maybe more," he said.

BBC Rome correspondent David Willey says it is unclear how the prime minister will manage to do both jobs.

Mr Berlusconi said Mr Ruggiero's repeated questioning of Italy's European policies had made life impossible.

"It was no longer possible for us to go forward like this, with us being forced to have our Europeanism tested every day," Mr Berlusconi said.

Italy is one of the pillars of Europe and one could be quite worried

French Finance Minister Laurent Fabius

France's questioning of Italy's euro-credentials came in a radio interview given by Finance Minister Laurent Fabius on Europe 1 radio station.

"Italy is one of the pillars of Europe and one could be quite worried," he said.

"I think there is a need for a clarification at the level of the heads of government.

"There needs to be an explanation. I think there needs to be a confirmation of the European commitment."

French Foreign Minister Hubert Vedrine also expressed his concern - calling Mr Ruggiero a "great European who enjoyed a very strong reputation across Europe".

All governments should have a favourable attitude towards the euro

Spanish Foreign Minister Josep Pique

Germany's Foreign Minister, Joschka Fischer, telephoned Mr Ruggiero to express his regret at his departure.

Meanwhile, Spanish Foreign Minister Josep Pique, whose country holds the rotating EU presidency, has postponed a planned trip to Rome for a week, at Mr Berlusconi's request, diplomatic sources said.

Mr Pique, whose original visit had been scheduled to include a meeting with Mr Ruggiero, had expressed the hope to meet Mr Berlusconi as soon as possible.

"All governments should have a favourable attitude to the euro," Mr Pique had told reporters.

Mr Berlusconi has faced continued criticism from inside Italy, where the euro hit a further hitch when bank workers went on strike on Monday.

Former prime minister Massimo D'Alema said Mr Berlusconi had done a "stupid thing" by demanding Mr Ruggiero's resignation.

Mr Ruggiero, one of the strongest pro-European voices in Mr Berlusconi's centre-right team, strongly criticised his cabinet colleagues last Thursday, for negative attitudes towards the European Union.

Euro's quiet arrival

The following day, Mr Berlusconi retorted that he was in charge of Italy's foreign policy, and Mr Ruggiero was merely a "technical" functionary carrying out his policies.

Italy was the only country participating in the currency not to organise celebrations for the advent of the currency at the new year.

One Italian minister has said he "couldn't care a hoot" about the single currency, and others have cast doubts over further European integration.

On Saturday, the European Commission said Italy was still trailing in last place in terms of euro cash transactions.