Scrutiny of Tehran’s role in allegedly attempting to influence the Iraqi poll has risen after a claim by King Abdullah of Jordan that more than 1m Iranians have crossed their 900-mile long border with Iraq.

Abdullah claimed last week that many of the Iranians were hoping to register and vote for pro-Iran Shi’ite parties.

“It is in Iran’s vested interest to have an Islamic republic of Iraq . . . that is very pro-Iran,” he told The Washington Post.

The king’s warnings were echoed by Ghazi al-Yawar, the interim Iraqi president, who claimed that Iran’s Shi’ite leaders were coaching Iraqi candidates and putting “huge amounts of money” into the campaign in the hope of producing a Shi’ite-led government.

The claims provoked outraged denials from the Iranian government and were played down by American and Iraqi officials who said that there was no evidence that so many people had crossed the border.

“The figure of 1m Iranians is highly exaggerated,” said Ibrahim al-Jafari, Iraq’s Shi’ite vice-president. “It is a huge number that is difficult to hide.”

Officials nonetheless acknowledged concern that the elections might produce what Abdullah described as a “crescent” of Shi’ite domination stretching from Iran into Iraq, Syria and Lebanon. “Strategic planners around the world have got to be aware that is a possibility,” Abdullah said.

Other experts suggested that Sunni leaders such as Abdullah and al-Yawar were inflating the Iranian threat to rally Iraq’s Sunni minority, which has been threatening to boycott the poll.

Last week leading Shi’ite parties made their first big push for power by presenting a unified list of 228 candidates. The list is supported by Ayatollah Ali al-Sistani, Iraq’s Shi’ite leader, but does not include supporters of Moqtada al-Sadr, the more militant cleric backed by Iran.

Despite continuing doubts about whether the election can be held amid current levels of violence, US authorities are pressing ahead with preparations. The prime minister, Iyad Allawi, a Shi’ite, suggested last week that the vote might have to take place over several weeks to police polling stations effectively. He said later that the elections should be held on January 30 as planned.

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