The NFL, which spent years criticizing researchers who warned about the dangers of football-related head trauma, has backed out of one of the most ambitious studies yet on the relationship between football and brain disease, sources familiar with the project told Outside the Lines. The seven-year, $16 million initiative was to be funded out of a $30 million research grant the NFL gave the National Institutes of Health in 2012. The NFL has said repeatedly that it has no control over how that money is spent, but the league balked at this study, sources said, because the NIH awarded the project to a group led by a prominent Boston University researcher who has been critical of the league. In a news release announcing the study Tuesday morning, Boston University said the NIH would pay for the project but made no mention of the NFL. The study seeks to capture what has been described as the holy grail of concussion research: the ability to diagnose chronic traumatic encephalopathy, or CTE, in living patients. Asked why the NFL did not want to fund the study, NFL spokesman Brian McCarthy on Monday referred questions to the NIH, writing in an email: "The NIH makes its own funding decisions." He did not respond to follow up questions. On Tuesday, McCarthy tweeted that the story was wrong. The NFL's decision not to fund the Boston University CTE study delayed its announcement for months, and the issue ultimately reached the office of NIH director Dr. Francis S. Collins, according to sources. As late as this week, some officials held out hope the league would change its mind, but the NIH remained committed to funding the project regardles The Foundation for the NIH, a non-profit organization that partnered with the NFL to administer the grant, released a statement late Tuesday morning that "the NFL was willing to contribute to the Boston University CTE study headed by Dr. Stern." The statement did not specify under what conditions the NFL was willing to participate, and a spokeswoman did not respond to immediate follow up inquiries. But sources told Outside the Lines that after Stern and Boston University passed a "scientific merit review" and received approval from an NIH advisory council of high-level experts last spring, the NFL raised objections to the selection. Dr. Walter Koroshetz, director of the NIH's National Institute for Neurological Disorders and Stroke, told Outside the Lines this week that he had asked the FNIH over a period of several months if the NFL would be providing funding for the study but never received a definitive response. He said he attempted to expand the study over the summer to include other researchers -- a proposal that might have satisfied the league. But the NIH ultimately decided to fund the study on its own. The FNIH statement said the NFL's overall funding commitment "remains intact." The NIH, according to the statement, will seek applications for an another study on CTE next year using NFL funding, which "will double the support for research in this area." When the NFL's "unrestricted" $30 million gift was announced in 2012, the NIH said the money came "with no strings attached"; however, an NIH official clarified the gift terms two years later, telling Outside the Lines that, in fact, the league retained veto power over projects that it funds. Koroshetz affirmed that this week.