Cosworth says that it as disappointed as Williams about their results this season - and has vowed to do everything it can to help improve the situation.
The British engine manufacturer has returned to Formula 1 after a three-year absence and, as well as supplying new teams Virgin Racing, Lotus and HRT, it wanted to use its tie-up with Williams as a benchmark to show that its power units are amongst the best in the sport.
But despite Cosworth exceeding its promised targets on peak power and fuel consumption, Williams has expressed some concerns about driveability and performance degradation over engine life.
Rather than shying away from the issues, however, Cosworth has admitted it is working flat out to make improvements - with the first major reliability upgrade to components having been introduced over the Monaco Grand Prix weekend.
Cosworth's general manager Mark Gallagher has welcomed the push being made by Williams to improve the situation - and thinks matters will be rapidly made better over the next few races.
"One thing we knew and the reason we did the deal with Williams was that we needed a benchmark team," Gallagher told AUTOSPORT. "So Williams' disappointment with the first five races is absolutely shared with Cosworth.
"We are disappointed, and they are disappointed, as the Williams-Cosworth package hasn't achieved what we wanted together."
While Cosworth believes tweaks to engine mapping will help a lot with the driveability issues, of bigger worry is the engine performance drop-off that has been experienced - and Gallagher has suggested that the matter could even require an FIA request for engines changes to be made
"We have seen a deterioration in performance and, as we are going through the lives of engines, we are able to measure this," he said. "We certainly have concerns that are sufficient for us to look to bolster our reliability of some components so we can ensure that the degradation is mitigated.
"The degradation problem is not by any means terminal for us, but what it does mean is that when the drivers drive the engines fresh they are seeing good performance that is falling away faster than they would like - and certainly faster than we would like. We are now in a position to measure that.
"We have also seen some component issues in the engine, and we do work with a lot of suppliers. We have one particular component, which I can't go into the details of because it is a fairly significant problem, but where one of the suppliers has provided a component that we were unable to test fully and there are now some issues with. And we have had to go through a number of changes.
He added: "For a team like Williams, every single thing that hampers its performance, given where it is, is serious.
"Having got off to a very good start, we are now in the thick of seeing just how hard a team like Williams and a driver like Rubens Barrichello, who are frankly only interested in podium finishes, have to push. And any areas where our engine isn't performing, we are having to step up to the mark. So the pressure is on and we have to work through a lot of those problems."
When asked if the problems could lead to an FIA engine upgrade request on reliability grounds, Gallagher said: "It is too early to say. We certainly have reliability concerns, and we are having to manage our engines very carefully.
"We are not compromising performance to any great degree, but we are keeping a very close eye on engine performance and engine degradation, and particularly the state of certain components in the engine because, if we see any warning signs, then we will pull an engine out of the pool."
Gallagher insists that both Cosworth and Williams must both share the burden for making the improvements to help lift their form.
"It is a question of working together," he said. "The exhausts for example are a Williams item, as is the aardvark [engine air intake], which is why we have to work with them hand in glove.
"In terms of ultimate performance, Williams has the potential at the moment to take us to the front. We are using Williams to put pressure on ourselves to deliver, because when Williams is not getting the results it wants it puts pressure on itself.
"We have responsibility to do everything we can to help Williams and that will be a good thing for when it is back to where it should be - which is in scoring points on a regular basis in the fight for podiums. For me, that is what is going to help us to guarantee our future and sell more engines to other teams."