The UK will spend at least an extra £100m on rebuilding Iraq, Foreign Secretary Margaret Beckett has said.
She said this would bring "total humanitarian and reconstruction support in Iraq" to £744m.
Working with the Iraqi government and "unlocking resources" within the country continued "to be a British priority", Mrs Beckett added.
She was speaking as an international conference on Iraq's future opened in the resort of Sharm-el-Sheikh, Egypt.
Delegates from 60 countries, including US Secretary of State Condoleezza Rice, are expected to sign a five-year International Compact for Iraq, promising to provide Iraq with support in return for reforms.
The United Nations-sponsored compact arose out of an Iraqi government initiative last year to establish a partnership with the international community.
Representatives of Iraq's neighbours, including Iran and Syria, are attending the two-day gathering, alongside members of the G8 group of rich industrialised nations and European Union states.
Making her announcement, Mrs Beckett said: "Our work with the Iraqi government, building their capacity and unlocking resources already available in Iraq's budget, continues to be a British priority."
She added: "The reforms and policies described in the compact are challenging.
"Their implementation can play a key part in helping the Iraqi government deliver essential improvements in security and services to the Iraqi people. "This will help reinforce the credibility of the national unity government and support greater stability in Iraq.