Barack Obama is expected to arrive in Baghdad this morning on the third day of his high-profile world tour, amid controversial remarks by the Iraqi leader that appeared to endorse the Democratic presidential candidate over his Republican rival.

On only his second visit to the country, Mr Obama will touch down hours after Nouri al-Maliki, the Iraqi Prime Minister, was quoted as saying that he backed the senator’s plan to bring home all US combat troops within 16 months. He implicitly criticised John McCain by saying that any effort to prolong the mission “would cause problems”.

The Obama campaign immediately trumpeted the remarks as proof that his Iraq plan had the backing of the country’s leadership. Mr al-Maliki’s interview with the German magazine Der Spiegel came one day after he and President Bush agreed to a “general time horizon” for withdrawal of US troops. It is the first time Mr Bush has even hinted at the idea of a timetable and reflects growing White House confidence, as well as increasing unhappiness in Baghdad over an open-ended US troop presence.

Within hours, however, a spokesman for Mr al-Maliki rushed out a statement 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”.

Ali al-Dabbagh said that the possibility of a US troop withdrawal was based on security improvements, echoing the White House.

Yet Mr Obama’s visit comes amid what appears to be growing consensus in Washington that the US can pull out troops at a far quicker rate than the White House had expected. Condoleezza Rice, the US Secretary of State, said that conditions in Iraq were improving “as we speak, so it’s not at all unusual to start to think that there is a horizon out there, in the not-too-distant future, in which the roles and responsibilities of the US forces are going to change dramatically”.

Mr Obama’s Iraq leg follows two days in Afghanistan and a visit to US troops in Kuwait, a trip shrouded in secrecy. He left the US on Thursday and his next destination is Jordan. There are meetings with the Palestinian and Israeli leaderships tomorrow.

After irritating Angela Merkel, the German Chancellor, with a request to make a speech in Berlin at the Brandenburg Gate - she found the proposal arrogant and distasteful - Mr Obama will now address a huge crowd on Thursday at the Siegessäule, or Victory Column. His aides say that he will discuss the need to strengthen transatlantic relations. He meets President Sarkozy in Paris on Friday, and Gordon Brown and David Cameron in London on Saturday.

Mr Obama has been taunted for months by Mr McCain for having visited Iraq only once and for never having set foot in Afghanistan. The Republican, who holds a large lead among voters over the issue of who would make the better commander-in-chief, continued to criticise his rival yesterday, accusing him of inexperience and arrogance. With fresh polls showing the two tied - and the US public split over whether to set a deadline for a troop pullout - he also reiterated his opposition to a withdrawal timetable. Mr McCain’s aides have described the foreign trip as a glorified campaign event, amid wide perceptions that it is aimed squarely at a US domestic audience to improve Mr Obama’s foreign policy credentials.

In an interview last night, Mr Obama rejected such accusations. He said that the object of the trip was to have “substantive discussions” with world leaders, “who I expect to be dealing with over the next eight to ten years. It’s important for me to have a relationship with them early”.

Mr Obama said the situation in Afghanistan, which will be his foreign policy priority, was “precarious and urgent”. He lunched yesterday with President Karzai, whom he criticised last week for not doing enough to help his country. He had breakfast with US troops and toured parts of the country by helicopter.

Mr Obama said that the improved security situation in Iraq provided the perfect opportunity to shift forces to Afghanistan, repeating his call for at least another 7,000 US troops there to tackle the growing insurgency. Mr McCain responded that his rival opposed the troop surge to Iraq last year.

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