Barack Obama arrived in Iraq today on the third leg of a world tour aimed at boosting his foreign policy credentials and convincing the US public that he has what it takes to become the next commander-in-chief.

The controversial issue of troop withdrawal was expected to feature highly in meetings between Mr Obama and a line of senior Iraqi, US and British officials during his 24-hour stay.

Mr Obama's itinerary was being kept secret but his first stop was in the southern oil-rich city of Basra, where some 4,000 British troops are still based, involved mostly in training Iraqi forces.

After a three-hour stopover, which included a meeting with Major-General Barney White-Spunner, commander of UK forces, he then flew on to Baghdad with two fellow senators, Jack Reed and Chuck Hagel.

The senator has pledged to pull all combat troops out of Iraq within 16 months if he wins November's presidential election. John McCain, his Republican rival, has given warning against a hasty withdrawal.

In Baghdad's Green Zone, Mr Obama and his Congressional colleagues held a one-hour meeting with Nouri al-Maliki, the Iraq Prime Minister. "We had a very constructive discussion," he told reporters afterwards before heading off to his next appointment in a large black Chevrolet Suburban bearning the warning sign: "Stay Back 100M".

Mr Obama's long-awaited visit follows a two-day trip to Afghanistan – the other key battlefield that the next president of the United States will have to handle.

He also stopped over in Kuwait last night, where thousands of US troops are stationed. The senator is next scheduled to travel to Jordan before spending the rest of the week in Europe, including a brief stay in London.

It is only the second time that the Democratic presidential hopeful has been to Iraq, a fact that Mr McCain often uses to question Mr Obama’s ability to understand the situation on the ground.

Mr McCain, in contrast, has been to the country eight times since the invasion.

He, unlike Mr Obama, was a staunch supporter of a 30,000-strong surge of US troops called for by President Bush last year when sectarian killings threatened to tip Iraq into civil war. The additional firepower is cited as one of the key reasons for a subsequent reduction in violence to its lowest level in four years.

In recent weeks, however, both US and Iraqi officials have started openly to warm towards the idea of US forces withdrawing from the country at a faster rate than previously expected.

Mr al-Maliki agreed with President Bush last week to set a "time horizon" for cutting US forces. It was the closest the Bush Administration has come to acknowledging the need for a timeframe for US troop reductions.

The Iraqi leader also made remarks in a German magazine that appeared to endorse Mr Obama’s vision of a 16-month exit over the policy of Mr McCain.

A spokesman for the Prime Minister, however, rushed out a statement yesterday saying that his remarks about Mr Obama had been “misunderstood, mistranslated and not conveyed accurately”, and that they “should not be understood as support to any US presidential candidate”.

In contrast to Mr Obama’s previous visit to Iraq in January 2006 as part of another congressional delegation that received scant media coverage, interest in his latest tour is huge. However, the senator’s every step is being carefully coordinated. No press conference is planned and media access will be minimal.

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