Speaking in Washington, Santos Silva promised a more detailed announcement during the summit on Syria that is to take place in the capital of Belgium in early April.

"Portugal, at the coming conference to be held on Syria, in Brussels, next month, will boost its financial contributions to humanitarian aid to Syria," he said.

In February of last year Portugal announced that it was contributing €25 million to the emergency aid effort in Syria.

Santos Silva made his comments in a break from a plenary session of the foreign ministers of the coalition that is combatting the jihadi group that calls itself Islamic State (IS). The coalition is made up of 68 countries and international organisations.

The atmosphere at the meeting was, he said, "optimistic, but not unrealistic". The ministers had "registered, and welcomed, the military retreat of the forces of Daesh" (the Arabic acronym also used to refer to the group) in Iraq.

"At this moment, more than 60% of the Iraqi territory that had been conquered by Daesh has been won back," he went on. "Daesh is losing the war in Iraq".

The meeting heard that there was a "similar" situation in Syria, with "more than a third of the Syrian territory that had fallen into the hands of Daesh ... recovered from it. So this mad, demented dream of the so-called caliphate is ever further from reality."

There remains, he stressed, "much to be done and the fight against terrorism is on various fronts".

The Washington meeting was the first of its kind organised by the new US administration of Donald Trump, who during his campaign to be elected president promised a new strategy to finish IS. But according to Silva, there has been no difference in approach under the new administration.

"What I saw, compared with the last meeting, was continuity," he said. "The same, very good logic of providing support to allies and the most detailed information possible, whether from a military or from a humanitarian point of view, and a very frank and very open exchange of ideas."

He also said it was notable that the new US secretary of state, Rex Tillerson, referred in his opening speech to imbalances between coalition members in terms of their military and aid contributions. Santos Silva acknowledged that these existed, but said that this was both on the military side - where the US footed the bill for 70% of the effort - and on the humanitarian side, where the other 67 states provided 75%, with European Union members accounting for the bulk of that.