Speculation about Mr Dehaene's prospects was fuelled by the Belgian daily Le Soir, which quoted an unnamed diplomat arguing that the lack of strong candidates to fill the post could help his chances.
Mr Dehaene, who announced that he is standing down as prime minister after his party received a drubbing in Belgium's general election on Sunday, might be backed by France and perhaps the United States, Le Soir said. The Belgian delegation to Nato yesterday declined to comment, adding only that it had read the reports "with interest".
Other delegations gave the idea a cool reception, partly because the last Belgian secretary-general, Willy Claes, was forced to resign after a corruption scandal which culminated in a trial last year.
One Nato diplomat said that "given the experience with Claes, I am not sure how good Dehaene's chances are, especially if you look at how scandal- ridden Belgium seems to be". Mr Dehaene came close to becoming president of the European Commission in 1994. His nomination was vetoed by John Major at the eleventh hour.
However, the speculation about his prospects for the Nato job demonstrates the extent to which a position is, in the words of one diplomat, "wide open".
Several potential contenders have been mentioned, including Michael Portillo and Sir Malcolm Rifkind, both former British defence secretaries, and Hans Haekkerup, Denmark's defence minister.
Germany had been expected to claim the post and to install either its current defence minister, Rudolf Scharping, or his predecessor, Volke Ruhe.
But Mr Scharping has told German newspapers that he is not very interested in the job and, at an EU summit in Cologne earlier this month, the German Chancellor, Gerhard Schroder, ruled both men out, saying categorically that there will be no German candidate.
Nevertheless, Nato diplomats remain unsure whether Mr Schroder's statement was definitive. "In this sort of decision, ruling people out doesn't always mean what it sounds like," said one Nato diplomat yesterday.
Mr Portillo, the former Thatcherite cabinet minister, has been canvassed by American diplomats who find his "Atlanticist" instincts and defence experience reassuring. The British government's approach appears ambivalent and neither Mr Portillo nor Sir Malcolm are likely to be promoted as candidates by the Government.
However, Tony Blair has said publicly that he would not veto Mr Portillo if others promoted his cause.
The current secretary general, Javier Solana, is due to leave within three months to take up a position as the EU's foreign policy supremo, leaving the 19-nation alliance some weeks to debate the issue. Mr Dehaene is affectionately known in Belgium as "the plumber" and "the bulldozer" because of his skill in weaving political compromises out of deadlock between Belgium's feuding linguistic groups.
But he resigned on Monday hinting that he would be happy to quit political life completely after overseeing the debacle of the dioxin-in-chicken scandal which triggered Europe's worst food contamination crisis since BSE. He has not personally been linked to any of Belgium's recent scandals.