Red Bull is not "out of the woods" despite other team members saying KERS is no longer a worry ahead of the Turkish grand prix.
The team's German-speaking faction Dr Helmut Marko and Sebastian Vettel said this week that, after earlier problems with the technology, modifications over the Easter break had eased concerns for Istanbul and beyond.
But Australian Webber is quoted by F1.com: "We are not out of the woods completely.
"The guys are working incredibly hard on it, but it will take time," Vettel's teammate added. "Let's say we are at 70 per cent now, so let's hope come the next few races we are all clear."
RB7 designer Adrian Newey is no fan of KERS, but he is determined to make it work in 2011.
"In 2009 it was possible to win the world championship without KERS," the Briton is quoted by Cologne Express. "Not now."