Sources opposed to Nato expansion have estimated that enlargement to embrace three new members will cost the US $10bn (pounds 63bn) and the European Nato members $40bn, but spread over about 15 years.
Britain pays about 20 per cent of the "subvention" to Nato, so on that basis the British taxpayer will pay about pounds 18bn over 15 years - equivalent to just under a single year's defence budget.
The US Congressional Budget Office puts the cost lower: $125 bn in total over 15 years, with the US paying around $19bn.
The greater burden will unquestionably fall on the new members - Poland, Hungary and the Czech republic - themselves. Hungary expects that joining the alliance will increase its military spending by 35 percent - from about $600m to $900m. Poland projects a 20 per cent rise, from $2.2bn to $2.75bn. If the Czech Republic has to make a similar increase - say 25 per cent - its spending will increase from about $770m a year to $930m.
Although upgrading the new members' armed forces to Nato standard will undoubtedly cost them money, supporters of enlargement argue it will still be cheaper than each state paying more to ensure its own security. That sounds reasonable, but it is impossible to compare those costs.
Accession to Nato does not mean that the new members have to buy western equipment, but their equipment is getting old and they will have to replace it anyway. Given the problems with Russian after-sales service, it makes sense for them to buy Western - or Israeli - equipment, which will open up an estimated pounds 22bn market.
As Jack Matlock, a former US Ambassador to Moscow said recently, "are free to buy American arms. The question is how they pay for it.
"If the American taxpayer finances them, it would be a direct subsidy to the arms industry. If they pay for them themselves, it could lead to real distortion in these countries' own budgets."Reuse content