US soldiers involved in the death of ITN journalist Terry Lloyd should be extradited to face trial in the UK, Lib Dem leader Sir Menzies Campbell said.
The inquest found Terry Lloyd was unlawfully killed
He said there was a "prima facie" case for unlawful killing, but the extradition agreement between the UK and US was a "one-way" process.
Tony Blair said it would be wrong to comment on whether an extradition application would be made.
Mr Lloyd was killed by a US Marine's bullet during the Iraq invasion.
He and three colleagues were caught up in a firefight between US and Iraqi forces near the Shatt Al Basra Bridge on 22 March 2003.
Mr Lloyd was shot in the head while in a makeshift ambulance. His interpreter was also killed and his cameraman is still missing, presumed dead.
A recent inquest into his death ruled Mr Lloyd was unlawfully killed - his widow Lyn has called it a "war crime".
At prime minister's questions, Sir Menzies, leader of the UK's third largest party, asked when the attorney general could be expected to make an application for the extradition and trial of the soldiers.
"For very obvious reasons, I think it would be very wrong for me to comment on anything the attorney general might do, in relation to that case," Mr Blair said.
"Once again however, I would like to send my deepest sympathies to Mr Lloyd's family."
Sir Menzies said "not much comfort there, I think" before adding "as recently as last night the government assured us that the extradition treaty with the US would facilitate justice.
"Isn't what we have a fast-track process that only goes one way?"
Mr Blair said Sir Menzies was "stretching reality a bit" and said it was wrong to discuss US, British or any of the coalition troops in Iraq, without mentioning they were doing "a superb job in very difficult circumstances".
"None of that will excuse anything wrong that's happened," he said.
"But I don't think it's right to have a debate on the armed forces when they are losing a significant numbers of troops, as the US forces are, without paying tribute to their courage and bravery."
A spokesman for the US Department of Defense said an investigation in May 2003 had found that US forces followed the rules of engagement.
"The Department of Defense has never deliberately targeted non-combatants, including journalists," he said.
"It has been an unfortunate reality that journalists have died in Iraq. Combat operations are inherently dangerous."