Earlier, the highly rated 21-year-old Dutchman said he would focus solely on his new Formula One role in 2013.
The reigning Formula Renault 3.5 series champion, Frijns had hoped to split his time between Sauber and a race cockpit in GP2 this year, but he said he could not put together the right budget for a competitive drive.
"We do it right or not at all," he told De Telegraaf newspaper last month.
But it is rumoured Sauber was unhappy that Frijns had turned down some offers to contest GP2 in 2013, believing its reserve driver should stay race-sharp if possible.
A source told Speed Week: "Money was not the problem, he could have driven for free. And we're talking about a really good team.
"Dozens of young drivers would do anything for such an offer."
Sauber team boss Monisha Kaltenborn confirmed that Sauber would like Frijns to race.
"In general, we have an interest in ensuring that our young driver is driving. Just as was the case in the past with Esteban Gutierrez.
"I have also heard that Robin turned down some good teams. Now he's coming to Bahrain and so I want to hear from him."
However, the very latest news is that Frijns has now agreed to race for the new Hilmer team in Bahrain.
"We hope that we can do the whole season together," said team boss Franz Hilmer.
Frijns denies he was pushed to accept the drive, denying that refusing to accept anything other than a top seat was a sign of arrogance.
"It had nothing to do with arrogance," he is quoted by formule.nl.
"With the other teams I had to bring money, and I didn't have it. Hilmer said I could drive in Bahrain for free, and I'd be crazy to refuse that.
"I just want to race.
"For now it's a deal just for one weekend, but hopefully now the story will go away that I feel too good for GP2. Of course that's nonsense," he insisted.