Eyebrows have been raised over the timing of the study's release, coming a day before the deadline imposed on the Greek parliament to pass legislation on reforms. Analysts said the IMF's advocacy of debt relief could now be a deal-breaker.
Moreover, the IMF has already reportedly signaled it could walk away from putting 16.4 billion euros of its own funds into a third bailout without some kind of debt relief, according to an IMF memo sent to European leaders last weekend and reported by the Financial Times on Wednesday.
"It's very interesting that the IMF has weighed in ahead of this vote," Adam Myers, European Head of FX Research, told CNBC Wednesday.
"When one of the creditors that is on the hook for 25 percent of the total bailout, says there needs to be an extension (of maturities) of that magnitude, it tells you that the plan that was agreed is unworkable.
Myers believed that some kind of "creditor acceptance of debt relief some time down the road in the next couple of weeks, "because without it, we'll be doing this again in a few months' time."
Ahead of Jack Lew's meeting with German Finance Minister Wolfgang Schaeuble, a well-known critic of Greece, one analyst said the deal could yet unravel with Greece without debt relief.
"If Germany wants the IMF on board it looks like it will have to give a lot more ground on debt relief or risk the agreement with Greece falling apart," Jasper Lawler, market analyst at CMC Markets said in a note Wednesday.
Lew's visit to Europe comes amid a fractious political environment in Greece ahead of the vote on reforms and nervousness in Europe over how the Greek parliament will vote.
Legislation on widespread reforms and spending cuts must be passed by the Greek parliament Wednesday for Greece to secure the third bailout. Predictably, hardliners in Tsipras' Syriza party are opposing more cuts and are expected to defect, meaning that a cabinet reshuffle is also likely in the next few days.
Read MoreGreek austerity vote: What to look out for
In a television interview on Tuesday, Greek Prime Minister Alexis Tsipras defended the 86 billion euro ($95.2 billion) bailout deal on Tuesday, saying the deal he struck with lenders at the weekend was necessary to avoid exiting the euro and that he had no alternative.
He also said, however, that he did not "believe in the deal," a comment likely to worry European creditors that are already distrustful of Greece's conviction to stick to a new bailout agreement.