I've spoken to aides of the Iraqi Prime Minister, Nouri al-Maliki, today and the official line on the kidnapping of the Iranian diplomat , Jalal Sharafi, is that it was committed, like dozens of other abductions, by rogue militants wearing Iraqi military uniforms. They are strenuously denying any involvement and it certainly makes no sense for it to have been an official operation.

Mr al-Maliki is caught in a very delicate position between the competing agendas of Iran and America, the regional and world superpowers. His Government has repeatedly stated that both allies of Baghdad and they must not play out their differences on Iraqi soil. It would be a huge mistake to inflame the already tense relations between Tehran and Washington.

Here in Baghdad the Iranian presence in Iraq is hard to see simply because of the physical limits of where we can safely go in the city. But that does not mean it's not there or on the wane. We hear about it mainly as a force behind the scenes and see it reflected in national politics, where Sunni groups accuse their Shia counterparts of being absolutely hand in glove with Tehran.

It's a game of influence, which, if you believe the American account, takes the form of funnelling weapons and money to secret underground militia groups, as well as entirely legitimate rebuilding and aid projects which the Iranian Ambassador to Baghdad has been talking about in recent days.

That picture changes as soon as you go to southern Iraq, where the Iranian influence is unmistakeable: the markets in Basra are flooded with Iranian goods and there is a huge amount of cultural similarity between the Shia communities in both countries.

I remember seeing a British map of southern Iraq officially marking the long frontier with Iran as a "Totally Porous Border". In a way it's a consequence of two centuries of Persian attempts to create a friendly Shia population in the region.

In the 19th century clerics in Najaf and the Iranian city of Qom were alarmed by the rise of Wahhabi fundamentalist Islam in modern-day Saudi Arabia and launched a deliberate campaign to turn southern Iraq into a Shia area to act as a buffer zone.

The result is that Iranian influence in Iraq is ingrained. The most senior Shia cleric in Iraq, Grand Ayatollah Ali al-Sistani, was born in Iran and speaks with a Persian accent. The leaders of many of the Shia political factions also spent years of the Saddam era in Tehran.

That means that Sunni MPs absolutely maintain, fairly or unfairly, that Shia leaders, including the Prime Minister, are hand in hand with the Iranian Government. For their part, Shia MPs are convinced that the Sunni groups are little more than Saddam's Baath party by another name. There is implacable mutual distrust between the two.

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