The US military has drawn up contingency plans to send American troops to Basra if Gordon Brown decides to pull out the entire British force, an American general revealed yesterday.

Britain still had “several missions” in southern Iraq, which the US expected it to fulfil. But if the Prime Minister withdrew all 5,000 remaining British troops, the US might have to “send some forces down there”, said Lieutenant-General Raymond Odierno, the second-most-senior US commander in Iraq.

That is the last thing the Bush Administration would want to do at a time when it faces growing domestic pressure to bring home troops, and the US military is already overstretched. A British withdrawal would be regarded in Washington as little short of betrayal.

Speaking to The Times and several American newspapers in his lakeside quarters near one of Saddam’s old palaces, General Odierno also said that he had reason to believe that the five British hostages who were seized from Baghdad’s Finance Ministry three months ago were still alive.

He chose his words carefully when asked about Basra, Iraq’s anarchic second city. He said he was comfortable with the British withdrawal from Basra Palace this week, noting that the Iraqi security forces had become a “bit more effective” and reinforcements would arrive within 30 days.

But questioned about the implications for the US military if British troops were withdrawn entirely from southern Iraq, General Odierno pointedly listed Britain’s continuing responsibilities there - maintaining a headquarters in the region, training Iraqi security forces, supporting the coalition’s political work, securing supply routes to the rest of Iraq and providing quick reaction forces. “There are still several missions we need them to do down there and we have laid it out for them,” he said.

“We believe right now that the British forces will stay there in some size. That’s what we have been told so far.”

But he acknowledged that a general election was looming, and disclosed that the US had drawn up contingency plans in case Mr Brown decided to withdraw the entire force: “One could be that we do allow the Iraqis to do most of it and don’t send anyone else down there. One could be that we send some forces down there.”

Basra has been unusually calm since the British withdrew from the palace on Monday. A British army spokesman said the city was quiet. Police said there had been no killings or kidnappings. Iraqi security forces are on the streets in large numbers, and the Iraqi police and Army, who usually steer clear of each other, are manning joint checkpoints. Residents said that the only gunfire heard in the city yesterday came from Iraqi soldiers celebrating their takeover of the palace.

General Odierno was speaking just days before General David Petraeus, the top US commander in Iraq, gives Congress his verdict on President Bush’s controversial “surge” strategy, which has resulted in 30,000 extra troops deployed to Iraq this year, bringing the total to 160,000.

The idea of expanding US operations further in Iraq would encounter fierce resistance in Washington at a time when Democrats, and some Republicans, are demanding a timetable for withdrawing US troops from a conflict that has cost 3,700 soldiers their lives and $10 billion (£5 billion) a week.

General Odierno said he received daily reports on the fate of the five British hostages, and added: “We have reason to believe they are still alive.” He refused to elaborate, and would not say whether there had been any contact with the kidnappers.

However, he confirmed that “rogue elements” of the al-Mahdi Army, a militia loyal to the radical Shia cleric Hojatoleslam Moqtada al-Sadr, were responsible. He challenged Hojatole-slam al-Sadr and his followers to prove that the ceasefire they announced last week - ostensibly to tackle the breakaway factions - was genuine by identifying the kidnappers. “Identify who these rogue elements are. Tell us where these hostages are. We think that’s something you can talk about,” he said.

One of the splinter groups is led by Abu Dera, an infamous Shia death squad leader who broke with Hojatole-slam al-Sadr last year after refusing to end his sectarian killing spree. General Odierno confirmed a report in The Times last week that Abu Dera was involved in the kidnapping.

Elsewhere in Baghdad yesterday the Iraqi Parliament reconvened after a month-long summer break, raising hopes that it could swiftly pass legislation promoting national reconciliation that Congress has demanded as a condition of keeping US troops in Iraq.

An Iraqi appeal court yesterday upheld the death penalty imposed on Saddam Hussein’s cousin Ali Hassan al-Majid, better known as Chemical Ali, for his role in massacring more than 100,000 Kurds in the 1988 Anfal campaign. He will be executed before the completion of his latest trial for crushing the Shia uprising after the 1991 Gulf War.

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