Bruins fan may wonder, quite reasonably, why the B’s haven’t yet signed Jarome Iginla to a contract extension. The answer is: They would if they could, but they can’t.

Iginla — one of the hottest goal-scorers in the NHL, with 10 goals in the last 10 games — will become an unrestricted free agent this summer. Bruins general manager Peter Chiarelli said yesterday he wants to keep the 36-year-old and has already had preliminary discussions on a new deal.

But nothing can be finalized now because of an NHL rule that, put simply, doesn’t allow teams to commit to future spending unless they have the future cap room freed up to cover it.

“It’s a function of cap space and ongoing multiple-year contracts,” Chiarelli said before his team’s 4-3 shootout win against the Flyers. “So it would have to wait ’til a minute after free agency begins (July 1). It’s an anti-inflationary thing. Basically it restricts you from going overboard on your future contracts. It prevents you from spending money you haven’t got.”

The B’s have $62.579 million committed for 2014-15, but the salary cap is expected to rise to just more than $70 million. Money will be tight, but getting Iginla re-signed is a priority for Chiarelli.

“He’s been terrific for us,” Chiarelli said. “He’s a veteran guy, he plays our brand of hockey and he fits in seamlessly with that first line. He’s been everything we thought he’d be — everything and more. I know Looch (Milan Lucic) and Krech (David Krejci) look up to him. There’s a good synergy on that line.”