Prime Minister Tony Blair has said the UK will "stand firm" in the face of the insecurity and bloodshed plaguing Iraq.
Blair has been criticised at home for taking UK to war
Mr Blair acknowledged that the Iraqi situation was "terrible", but he said there was a clear choice to make between right and wrong there.
He was speaking as families of two US and one British hostage waited for news from Baghdad after a deadline set by their kidnappers passed.
The captors said they wanted all Iraq's female prisoners to be freed by Monday.
"Our response has not got to be to weaken. Our response has got to be to stand firm," Mr Blair said in comments to journalists at Downing Street.
"Whatever the differences over the Iraq conflict, there is a clear right and wrong on these issues, and that is to be with the democrats and against the terrorists," Mr Blair added.
The families of three hostages - Briton Kenneth Bigley and Americans Eugene Armstrong and Jack Hensley - have been on television pleading with the captors, who seized the men in a smart Baghdad suburb last Thursday.
The British embassy in Baghdad has set up a hotline for information about the men after a Foreign Office official appeared on Arabic television to ask Iraqis for help.
The hostages are reportedly held by Tawhid and Jihad (Unification and Holy War), a group headed by a suspected al-Qaeda leader Abu Musab al-Zarqawi.
Meanwhile, 18 Iraqi national guardsmen seized by another Islamist group were freed on Monday.
The three were seized in their Baghdad house last week
The Arabic TV station al-Jazeera aired a videotape apparently showing the men wearing traditional white robes and holding Korans.
The militants had demanded the release of Hazem
al-Aaraji, an aide of the radical Shia cleric Moqtada Sadr, detained by US forces over the weekend.
In other developments:
- A Sunni cleric, Sheikh Muhammad Jadwa, is killed in Baghdad, less than 24 hours after another Sunni cleric, Hazem al-Zaidi, is kidnapped and killed. Both were attacked in Shia areas of the city.
American warplanes bombard the northern part of the city of Falluja, a rebel stronghold west of Baghdad.
- A car bomb explodes in the northern
city of Mosul, killing three people.
- Iraqi security forces conducting a raid near Nasiriya free a Jordanian civil servant who was kidnapped last month.
More than 100 foreigners have been abducted by insurgents in Iraq over the past 17 months, in a bid to destabilise the US-backed interim government and drive foreign troops out of the country.
On Sunday, an Islamist group said it had beheaded three members of the pro-US Kurdistan Democratic Party.
A video published on the internet by the Army of Ansar al-Sunna apparently showed the men's heads being sawn off and placed on their bodies.
Hostages currently held include two French journalists abducted almost a month ago and two female Italian aid workers kidnapped along with two Iraqi colleagues on 7 September.
Tawhid and Jihad group has taken foreign hostages before in Iraq and three of them - including US citizen Nick Berg - have been killed when the group's demands were not met.