High-powered "Star-Wars"-style lasers could be coming to military vehicles within a few years.

Or it could be decades. Or centuries.

As part of their research budget pitch to Congress on Wednesday, dDefense dDepartment officials professed confidence that long-promised "directed energy weapons" are in the reach of military experts in the near future, noting recent technological progress and the current use of defensive laser systems in some service aircraft.

But they also acknowledged that's a promise that lawmakers have heard many times before.

"Directed energy is always something that is five years away, and then years later it's still five years away," said Stephen Welby, assistant defense secretary for research. "But I'm very excited about what's happening in these spaces now."

The sales pitch underscored the promise and pitfalls of the annual defense research budget. Next year's request is nearly $72 billion — about 12 percent of the total fiscal 2017 defense funding request — and offers the hope of cutting-edge medical advances, innovative intelligence tools and science-fiction dreams like laser blasters.

It also comes with a lot of unfulfilled projects and deadline caveats, at a time when every dollar is under closer scrutiny from the conservative-led House and Senate.

Key congressional leaders have indicated they want more money for defense spending than the White House's proposal, but have also promised to root out waste and inefficiency in Pentagon operations. Ambitious but unlikely technology projects that run into the tens of millions often end up as punchlines in lawmakers' campaign materials promising to clean up Congress.

On the laser front, Air Force officials have outlined plans to start competition to develop systems for the service's fighter fleet, with a public goal of firing a weapon from a tactical aircraft by the end of 2021. Army and Navy officials offered similar, less specific plans to lawmakers for their own platforms.

And the lasers weren't close to the most imaginative projects teased by defense researchers Wednesday.

Arati Prabhakar, director of the Defense Advanced Research Projects Agency, testified about experimental radar systems that respond in real time to enemy detection efforts, prototypes of cameras that detect light patterns to uncover past and present troop movements, and a proposed mini-mobile medical lab to diagnose a variety of diseases within 30 minutes.

But turning any of those ideas into reality — if they can even be turned into reality — will take money, and DARPA’s nearly $3 billion annual budget has seen cuts in recent years. Officials are hoping for a $105 million increase in fiscal 2017, a tiny sliver of total defense spending, but still a sizeable sum of money.

Lawmakers from the House Armed Services Committee hearing offered general support for the research work, but warned they still have concerns. Several asked about how the various research agencies communicate to ensure they aren't duplicating work.

Rep. Joe Wilson, R-S.C., chairman of the subcommittee on emerging threats, worried that many of the ideas have simply run out of time.

"As I see it, starting major initiatives at the end of an administration makes it difficult to ensure that these things will survive the new budgetary and policy priorities that will naturally arise with a new president," he said. "I hope I am wrong, since I support many of the things being proposed in this budget request, but only time will tell."

Lawmakers are expected to revise the president's budget request over the next few months, in hopes of passing a new defense appropriations measure before the November elections.

Leo Shane III covers Congress, Veterans Affairs and the White House for Military Times. He can be reached at lshane@militarytimes.com.