Maybe they are hinting at lending their support to the report being refered to the UNGA or even the UNSC unless Israel uses its "get out of prison" card. The US wouldn't like to use its Veto Power, but it will have to if it reaches the UNSC. After Clinton's gaffe, regarding Israel's ongoing illegal settlement constructions, it wouldn't look good. France and Britan wont, that's what they just said, in so many words.
Greek PM says may have to call early election (Reuters)
from the article: U.K., France want Israel, PA to probe Goldstone war crimes claims