south to the stark mountains of the north.
By Jack Fairweather in Tuwella
Iraqi officials fear that the big winner from next month's historic election will be its powerful neighbour and former enemy, Iran.
The countries share a 1,000-mile border, stretching from the flat desert wastes and marshes of the south to the stark mountains of the north.
There are plenty of innocent travellers crossing the frontier: pilgrims on their way to visit Shia Muslim holy places, or people with family and friends on the other side, a result of Saddam Hussein's relentless purging of the Shia majority in Iraq.
In the region around the mountain town of Tuwella they rarely bother using the official crossing, a time-consuming and costly enterprise, instead simply walking over the hillside above the town.
There are, however, less innocent visitors. Officials of Iraq's interim government maintain that hundreds of Iranian agents have infiltrated the country and joined the insurgency in an attempt to keep American forces unbalanced.
At the same time, they say, Teheran is maintaining a stranglehold on Shia political parties in Iraq.
The two largest, the Supreme Council for Islamic Revolution in Iraq and the ad-Dawa party, spent decades of exile under Iranian tutelage and have formed a single voting bloc for the Jan 30 poll. Many analysts expect them to command a majority over the secular party led by the interim prime minister, Iyad Allawi, and officials fear Iran will be sitting pretty, with a pliant government of a strong Islamic bent in Baghdad.
"There is a real concern that the interference we are seeing from Iran at the moment is just the beginning, and that Baghdad could be slowly slipping into the orbit of Teheran," said Safa Rasul, chief of staff of Iraq's National Security Council.
Iraqi leaders from all sides called for calm yesterday after Sunday's suicide attacks which killed more than 60 people. The elections would take place on time, they promised.
But amid concerns over the dire security situation, Iraq, with its traditional ruling Sunni elite, continues to be uncomfortable with its powerful neighbour, the largest Shia nation.
The war between the two in the 1980s, one of the bloodiest fought anywhere, began with an Iraqi invasion after it accused Iran of making a land grab.
In the Kurdish-controlled north officials say they have intercepted a steady stream of fighters from the terrorist group Ansar al-Islam, which they say Teheran has sheltered since the US-led invasion to topple Saddam.
"Iran is continuing to work with Ansar," said one senior Kurdish official, who believed there were 1,500 members working in Iraq for the Ansar group, an affiliate of al-Qa'eda.
"They are trained and recruited across the border for terrorist attacks in the south of Iraq," said the official.
For their part, US officials in Baghdad see Teheran as playing a more ambivalent role in Iraq's insurgency.
They agree that money and weapons are crossing the border, but say the support is coming from individual clerical organisations, rather than representing a concerted government policy, a reflection of Iran's joint rule by government and religious bodies.
"We believe some ayatollahs have taken an active role, others have not. They're waiting to see what happens, with a finger in every pie," said a senior American official.
Privately, officials concede that Iraq is likely to take "an Iranian turn" after the election, a notion unimaginable before the invasion, when neo-conservatives in Washington believed they could create the Middle East's first secular democracy.
Now many grudgingly accept that the elections are likely to usher in an Islamic state.
The south, where most of the Shia majority live, already has a strong Iranian and Islamic tone.
As in Iran, religious law imposed by the Hawsa, the Shia clerical body, now rivals secular courts. Religious parties, often with militia backing, hold considerable sway over local government.
There are hundreds of Iranian operatives in the south, known simply as ittila'at - the Persian word for intelligence.
One group, Thar-Allah, was set-up with Iranian money and openly pledges its loyalty to Grand Ayatollah Ali Khamenei of Iran.
The Supreme Council for Islamic Revolution and ad-Dawa party play down their Iranian roots although they are none the less prevalent.
Both parties were forced into exile in Teheran by Saddam in the 1970s and early '80s. In 1983, the Supreme Council, under the tutelage of the late Ayatollah Mohammed Bakr al-Hakim, formed the Badr Brigade from Iraqi exiles.
The brigade, trained by Iran's Islamic Revolutionary Guard Corps, fought on Iran's side during the Iran-Iraq war. Since returning to Baghdad in 2003, and for some time before that, the Supreme Council's call for an Islamic revolution along Iranian lines - as the name of the organisation suggests - has been softened.
But asked what level of influence Iran has over the parties, one western diplomat replied: "Vast. In the south of the country the whole idea of Iraqi nationalism has broken down. There's a strong sense of community with Iran."
The Supreme Council and ad-Dawa recently formed the United Iraqi Alliance with several smaller Shia parties with the approval of Iraq's senior Shia cleric, Grand Ayatollah Ali al-Sistani.
According to his aides, the Iranian-born ayatollah wants an Iraqi state that strongly encourages Islamic law in all aspects of life, from controlling women's dress and mandatory prayer lessons in schools to Islamic codes of marriage and inheritance, without the overpowering Islamism of the revolutionary regime in Iran.
The effect of Shia dominance in government after the elections is likely to reduce Iran's support for cross-border terrorism, say some Iraqi officials.
"We're going to see a lot less violence when Teheran no longer feels threatened," said the Kurdish interior minister, Saeed Othman.
Back in the frontier town of Tuwella, Omar Ali, who regularly crosses the border to visit family members, cracks one of the locally grown walnuts between his hands at his greengrocer's shop, and ponders Iraq's future.
"We used to have a lot of trade with Iran. They haven't always been our enemies," he said.