The government needs to explain its Iraq policy to Parliament, the Lib Dem leader Sir Menzies Campbell has said.
Sir Menzies said the government's Iraq policy had 'failed'
The policy had "failed" and the Iraqi people had to take "responsibility for themselves", he told BBC Radio 4's PM programme on Monday.
Iraq deputy PM Barham Saleh said his country still needed the international community to help fight extremists.
"We need to work together to ensure that that day will come when Iraqis are fully in charge of security," he said.
But Sir Menzies, referring to the continuing presence of British troops in the country, said: "I think it's clear, everyone now accepts... that this can't be without limit of time."
He said: "There is a moral obligation - even those of us who were opposed to the war accepted a moral obligation to the people of Iraq - but it can't be open-ended.
"It's got to be somehow reflected in Iraqi government and in the Iraqi people taking responsibility for themselves."
He said the government needed to explain to Parliament and the UK public what was happening, as there had not been a debate on Iraq for two years.
At the weekend US President George W Bush said military tactics in Iraq would keep changing to deal with insurgents, but the US would not abandon the goal of building a strong democracy.
The issue of Iraq, and possible changes in strategy have been increasingly high profile in the US ahead of the elections next month for Congress.
Sir Menzies, who said the US elections were prompting a close analysis of the US-Iraq policy, said: "I think the strategy has failed. The prime minister and the president of the United States are the only two people who say it hasn't."
Earlier, Downing Street denied that Mr Blair had pressed Mr Saleh for assurances his forces could take over policing south Iraq within a year.
Mr Saleh said it would not be possible to build a "totally professional security organisation" in a short period of time.
He told BBC News 24: "We are making progress, but for some time to come we need the help of the coalition.
"We recognise that Iraqis must assume responsibility - this is the view of the government of Iraq and it is important that we share the same view as the coalition.
"We need to work together to ensure that that day will come when Iraqis are fully in charge of security.
"This is our country, we know the culture better, we know the environment better and we have to assume responsibility for the security of our country," Mr Saleh said.
Foreign Secretary Margaret Beckett said once the Iraqi government could "cope", then UK troops would leave, but stopped short of giving a deadline.
Mrs Beckett, who met Mr Saleh on Monday, said there would be no "rash" promises about troop withdrawal.
Mrs Beckett, responding to comments by Defence Secretary Des Browne and Foreign Office Minister Kim Howells, who have both suggested recently that local forces should be able to take over within a year or so, said: "It would be a mistake to set some kind of false deadline. This is going step by step as it is possible and practicable to move forward."
Asked what sort of Iraq she envisioned being left behind, she said one that was democratic, which could "cope" and that was "back on its feet".
Pressed on whether it would be a disaster if Iraq split up, Mrs Beckett replied: "If that is what they want and they feel it is workable that is another matter."