Signatories to yesterday's open letter come from both ends of the political spectrum. They include former US arms negotiators, Paul Warnke and Paul Nitze; Michael Mandelbaum, a former foreign affairs adviser to President Clinton; Jack Matlock, who was ambassador in Moscow during the collapse of communism and several other former ambassadors with experience of the region.
The letter was co-ordinated by Susan Eisenhower, granddaughter of the former US president, Dwight Eisenhower, and a leading foreign affairs analyst in her own right.
The letter, published 10 days before the Nato summit meeting in Madrid, where the new members are expected to be approved, is the latest and strongest indication of a gathering head of steam in the United States against expansion of the alliance.
Not mincing its language, the letter describes Nato enlargement as a "policy error of historic proportions" that would "decrease allied security and unsettle European stability". The arguments relate to Russia, to the aspiring Nato members, to the alliance and to the US.
With Russia, it argues that expansion will strengthen conservatives - who will see Russia's security threatened - and prevent ratification of outstanding arms control treaties, including Start II. In Europe, it says that enlargement - whether with Poland, Hungary and the Czech Republic, as the US Administration favours, or with the addition of Romania and Slovenia, as some European countries favour - will establish a new division in Europe between those who are in and those who are out.
Of the alliance, the letter argues that its military effectiveness will be diluted, and commit Nato to defending countries whose democracy and ethnic relations are not yet settled. And as far as the US is concerned, the signatories argue that the European Nato members, old and new, will expect the US to pick up the bill, a bill which will be perhaps five times more than the $25bn (pounds 15bn) State Department estimate.
Unusually for an initiative that originates in the charmed circles of the Washington elite, the arguments advanced in the letter reflect a large and growing segment of American opinion outside Washington. Less sophisticated as the arguments of Washington-insiders, the view from the "heartland" concentrates on the likely cost to American taxpayers of equipping central European countries for Nato membership and the basic principle of whether American soldiers should be expected, as it is said, "to die for Danzig".
Business concerns, on the other hand, stand by the administration's support for expansion, partly because of the weapons orders they expect to gain when Central Europe has to make its weapons systems compatible with those of Nato.
Despite this support, yesterday's letter provides a salutary warning to the administration of the opposition Nato expansion is likely to face when it comes before the US Senate for ratification. Mr Clinton's special adviser on Nato enlargement, Jeremy Rosner, already concedes that the necessary two-thirds majority will not be easy to obtain.
Even prominent supporters of enlargement, such as Democrat Senator, Joe Biden, cautions that younger senators do not have the emotional attachment to Europe of their elders.Reuse content