British diplomats did not make any concessions to secure the release of the 15 UK sailors detained last month by Iran, Tony Blair has said.
Speaking outside Downing Street, the prime minister told reporters that the return of the personnel did not involve any "deal" or "negotiation".
He expressed his belief that a combination of maintaining a "calm and firm" stance, which maintained bilateral communication while mobilising international opinion in Europe and at the UN, ensured the safe return of the sailors to Britain.
Mr Blair launched a wider attack on the Iranian government, maintaining Britain's unmoving stance against Tehran.
He referred to the deaths of four British soldiers in the southern Iraqi city of Basra earlier today in the same breath as criticising Iran for supporting terrorism in Iraq.
Mr Blair said their deaths demonstrated the "sober and ugly reality of what is happening through terrorism in Iraq".
"Now it is far too early to say that the particular terrorist act that killed our forces was an act committed by terrorists who are backed by any elements of the Iranian regime so I make no allegation in respect of that particular incident but the general picture … is that there are elements of the Iranian regime that are backing, financing and supporting terrorism in Iraq," he said.
The prime minister remained optimistic about future prospects for negotiating with Tehran, however, explaining that the captured-sailors affair had opened up lines of communication which had not previously been available to British diplomats.
"I think it is insensible that we pursue those channels of communication," he said.
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