Britain says it is doing everything it can to secure the release in Iraq of British hostage, Kenneth Bigley.
Ken Bigley was shown sobbing behind bars
UK Prime Minister Tony Blair said his government would respond "immediately" to any contacts from the militants.
However, Mr Blair's office later said there was a clear distinction between responding and negotiating, ruling out any deals with the hostage-takers.
The militants earlier aired a new video showing Mr Bigley shackled in a cage and pleading for help from Mr Blair.
"Tony Blair is lying. He doesn't care about me," Mr Bigley sobbed, dressed in an orange jumpsuit and looking unwell and distraught.
The video of Mr Bigley was screened on Wednesday on the Arab television station al-Jazeera.
It was aired a day after two Italian women aid workers and four Egyptian engineers were freed by their captors in Iraq.
Italian Foreign Minister Franco Frattini said no money had been paid for the release of Simona Pari and Simona Torretta, both 29.
But chairman of the Italian parliament's foreign affairs committee Gustavo Selva described the denial as purely "official", saying that he believed that a ransom of $1m or more was paid for the release.
Blair says no contact has been established with the kidnappers
"We can't make contact with them and they have made no attempt to make contact with us," Mr Blair said on the fringes of his Labour Party's annual conference in Brighton.
"If they made contact with us, it is something we would immediately respond to," the prime minister said.
Mr Blair said he was "absolutely sickened" by what had gone on.
Mr Blair's office was quick to clarify that this did not mean that London was offering to negotiate, the BBC's political correspondent Jon Devitt reports.
A spokesman stressed that there could be no deals and no negotiations, but said the government might be able to find out things like whether Mr Bigley was still alive or where he was being held.
In the footage Mr Bigley calls on Mr Blair to meet the demands of his kidnappers to free female prisoners in Iraq and says his captors do not want to kill him.
16 Sept: Two Americans and Ken Bigley taken hostage
18 Sept: All three appear in video with captors
20 Sept: American Eugene Armstrong beheaded
21 Sept: American Jack Hensley beheaded
22 Sept: Ken Bigley appears on video, appealing for help from Tony Blair
29 Sept: Second video plea made by Bigley
Following the broadcast of the video, Mr Bigley's family renewed their appeal for the release of the 62-year-old engineer.
"We would like to send a message, on behalf of our family, to the people holding Ken... We want to thank you for this opportunity to see him alive again," said Mr Bigley's brother Philip.
"Please could you pass on once more our love and thoughts to him."
On Thursday Mr Bigley's Thai wife, Sombat, also made a new appeal for his captors to show mercy, and for Mr Blair to come to his aid.
"Tony Blair could help him hugely," she told the Reuters news agency.
The British government says it has no female prisoners in its custody in Iraq.
Al-Jazeera said the station had received the video anonymously.
Mr Bigley was taken hostage in Baghdad two weeks ago by the hardline Tawhid and Jihad group along with two American colleagues who have since been beheaded.
He has appeared in videos before, including on 22 September when he pleaded for his life.