Smuggled and bootlegged, it has been the cause of transatlantic tensions for more than two decades. But after 21 years in exile, the haggis is to be allowed back into the United States.

The "great chieftan o' the puddin-race" was one of earliest casualties of the BSE crisis of the 1980s-90s, banned on health grounds by the US authorities in 1989 because they feared its main ingredient ‑ minced sheep offal ‑ could prove lethal.

Some refined foodies might insist it always has been and always will be: in the words of Robert Burns, in his Ode to a Haggis, looking "down wi' sneering, scornfu' view on sic a dinner". But now, as millions of Scots around the world prepare to celebrate Burns's legacy tonight with an elaborate, whisky-fuelled pageant to a boiled bag of sheep innards, oatmeal, suet and pepper, its reputation has been restored, on health grounds at least.

For the past two decades, Americans of Scottish descent ‑ of whom there are at least 6 million ‑ have been forced to celebrate Burns' night without a true haggis, much to their distress.

There are stories of Scots smuggling in a haggis for their starving cousins, risking deportation in the process. Others are said to have secretly tried to create homemade, bootleg haggis, desperate to sample that particularly peppery concoction.

Meanwhile, butchers in the US have tried, and failed, to make their own versions of the pudding without using the vital ingredient: sheep. "It was a silly ban which meant a lot of people have never tasted the real thing," said Margaret Frost, of the Scottish American Society in Ohio. "We have had to put up with the US version, which is made from beef and is bloody awful."

The long-running campaign by Scottish ministers to reverse the ban has been reinvigorated by Alex Salmond, the Scottish National party leader, since he became first minister, privately lobbying US officials during his visits there. The reverse in policy from the US department of agriculture is now expected by Salmond's government after the World Organisation for Animal Health decided that sheep lungs no longer carry a risk of contamination by scrapie, a close variant of mad cow disease, or bovine spongiform encephalopathy.The latest sales figures suggest haggis is more popular now than ever.

Nearly £9m worth were sold in the UK alone last year, the 250th anniversary of Burns' birth, up by 19% on 2008. Richard Lochhead, the Scottish environment secretary, was delighted. "I am greatly encouraged to hear that the US authorities are planning a review of the unfair ban on haggis imports," he said. "We believe that reversing the ban would deliver a vote of confidence in Scottish producers, and allow American consumers to sample our world-renowned national dish."