Beckham can be replaced near start of the World Cup
Eriksson will be delighted at being given such room for manouevre as Beckham battles to recover from a broken foot.
The news gives Eriksson an extra nine days to assess Beckham's fitness before making a final decision on his availability.
Eriksson had been expecting Fifa to rule that only `new' injuries would enable teams to replace players after they had submitted their official squads on 21 May.
However, Fifa insists that their initial statement, which was then clouded in some uncertainty, was correct in asserting that Beckham could be replaced before 30 May as long as an independent doctor agreed he was injured.
There are two different clauses in the Fifa regulations, one of which would appear to point towards an injury only being allowed in cases of `force majeur', or, in other words, unforeseen circumstances.
But Fifa spokesman Andreas Herren said: "The regulations are interpreted that it doesn't make any difference whether the injury is new, old or recurring as we know coaches would not use it as a tactical ploy.
"If the England team were to nominate David Beckham in their squad in the hope he would regain full fitness before the tournament and then that was not the case, they could use a medical certificate to call up a replacement player."
This would only be possible until up to 24 hours before the start of the tournament, which kicks off on 31 May with the opening game between France and Senegal.
The FA confirmed they had been informed of this latest ruling by Fifa, with the world governing body now expected to circulate it to all competing nations to prevent any chance of a challenge or appeal in the build-up to the tournament.