International credit rating agencies on Monday gave their top grade to Europe's sovereign bailout fund, but the move failed to halt the strain on the ailing government bonds of Ireland and Portugal. The European Financial Stability Facility, as the fund is known, was rated AAA by Moody's Investors Service, Standard & Poor's and Fitch Ratings. The ratings are preliminary because no member state has yet called on the facility for help, and it has thus issued no debt. 'The central scenario for me and euro zone finance ministers is that we don't need to become operational,' Klaus Regling, the stability fund's chief executive, told Reuters on Monday. He said there was no point in the fund's issuing bonds unless and until it was called upon to help a member state. The facility, announced May 9, is essentially the sum of the commitments of euro zone governments to finance a bailout. It works out to 440 billion euros, or $575 billion, with Germany, Europe's biggest economy, responsible for the largest contribution, at about 123 billion euros. When an additional commitment from the International Monetary Fund is included, Europe has about 750 billion euros to help governments in danger of defaulting. Debt concerns began hurting investor confidence last year, when Greece acknowledged having for years disguised the poor state of its public finances. Those concerns have resurfaced in recent months, with many investors convinced that some smaller euro zone members will not be able to pay off their creditors without at least some form of debt restructuring. Ireland's 10-year government bonds rose 26 basis points Monday, to 6.39 percent, while Portugal's rose 36 basis points, to 6.35 percent. A basis point is equal to one-hundredth of a percentage point. Both countries face a test of market appetite when they sell bonds this week. Greece's 10-year bonds are at 11.44 percent, despite support in the secondary market from the European Central Bank. Its unprecedented buying of such debt was another of the crisis measures announced May 9. The gap, or spread, between those bonds and German bonds -- which are considered the safest in Europe -- has risen to record levels. Dietmar Hornung, senior credit officer in Moody's sovereign risk group, noted in a statement that any debt issued by the facility would be backed first by the beneficiary member state's promise to repay, then by the major AAA-rated commitments of Germany, France and the Netherlands, as well as other euro zone members with lesser ratings. Still, the facility's grade could be endangered if any of the three AAA-rated countries was to be downgraded or if they wavered in their support, the agencies warned. Default on bonds issued by the facility would have grave consequences for Europe, Hornung said: 'Apart from threatening the survival of the European Monetary Union, it would also result in considerable reputational risks for core European countries like Germany and France, and would likely increase their borrowing costs.' 