Legal action is being taken against 15 Royal Navy personnel held captive by Iran for "entering Iranian waters", a senior Iranian diplomat has said.
The crew has been held captive for more than a week
Gholamreza Ansari, Iran's ambassador to Moscow, said "legal process" had started but denied reports which quoted him saying the group may face trial.
The UK government says the captives were seized in Iraqi waters and is demanding their "immediate" return.
Foreign Secretary Margaret Beckett said Mr Ansari's comments were "unhelpful".
Iran's official IRNA news agency earlier carried a report saying the envoy had told Russian television that legal moves against the 15 had already started and that there was a possibility they could stand trial.
But the agency later quoted Mr Ansari saying the television channel had made a "translation mistake" when quoting him saying the group could face charges and a trial.
Britain denies Iran's claims that the UK crew was in its waters when seized on 23 March and is demanding their "immediate" return.
UK VERSION OF EVENTS
1 Crew boards merchant ship 1.7NM inside Iraqi waters
2 HMS Cornwall was south-east of this, and inside Iraqi waters
3 Iran tells UK that merchant ship was at a different point, still within Iraqi waters
4 After UK points this out, Iran provides alternative position, now within Iranian waters
Speaking at a European Union meeting in the German city of Bremen, Mrs Beckett said she wanted a swift diplomatic solution to the crisis.
"I think everyone regrets that this position has arisen. What we want is a way out of it - we want it peacefully and we want it as soon as possible," she said.
Mrs Beckett confirmed that a British diplomatic note had been sent to the Iranians, but gave no detail of the contents.
She also expressed "concern" about claims by Mr Ansari that the British personnel could face legal action.
"I don't think it's helpful to Iran, I don't think it's helpful to our detainees - I think that is not the tone really that I would wish anyone to strike," she said.
But she added that things had "gone a little quieter" in the negotiations and she hoped that was "a good sign" that Iran was "thinking afresh what is the way out of this situation".
IRANIAN VERSION OF EVENTS
1 Royal Navy crew stray 0.5km inside Iranian waters
2 Iran gives set of co-ordinates to back up their claims
3 According to seized GPS equipment, the Royal Navy crew had previously entered Iranian waters at several other points
4 Iran informs Britain of the position where the crew were seized, inside Iranian waters
Earlier, US state department spokesman Sean McCormack rejected suggestions that a swap could be made for five Iranians captured in Iraq by US forces in January.
The Iranians, believed to be members of the Revolutionary Guard, were taken in a raid in the city of Irbil, along with equipment which the Americans say shows clear Iranian links to networks supplying Iraqi insurgents with technology and weapons.
US officials have condemned Iran's actions over the 15 Navy personnel and publicly supported the UK.
And European Union foreign ministers, meeting in Bremen, Germany, called for "the immediate and unconditional release" of the sailors and expressed "unconditional support" for Britain's position.
Prime Minister Tony Blair has also criticised Iran for "parading" the UK crew on television in a way which would only "enhance people's sense of disgust".
In what appeared to be an edited broadcast on an Iranian channel on Friday, captured sailor Nathan Thomas Summers said: "I would like to apologise for entering your waters without permission."
He was shown alongside two colleagues, one of whom was Leading Seaman Faye Turney, from Shropshire, who had been broadcast apologising to Iran earlier in the week.
A letter, allegedly from LS Turney, was released on Friday in which she said she had been "sacrificed" to UK and US government policy.
Along with LS Turney and Nathan Summers, who is from Cornwall, they are Paul Barton from Southport, Danny Masterton from Ayrshire, Joe Tindell from south London and Adam Sperry from Leicester are among the captured personnel.
The Britons, based on HMS Cornwall, were seized by Revolutionary Guards as they returned from searching a vessel in the northern Gulf.