WASHINGTON—Regulators are proposing new rules on Internet traffic that would allow broadband providers to charge companies a premium for access to their fastest lanes.

The Federal Communications Commission plans to put forth its rules on Thursday. The proposal marks the FCC's third attempt at enforcing "net neutrality"—the concept that all Internet traffic should be treated equally.

Developed by FCC Chairman Tom Wheeler, the proposal is an effort to prevent broadband Internet providers such as Comcast Corp., Verizon Communications Inc., and Time Warner Cable from blocking or slowing down individual websites served up to the consumer. The idea is that consumers should be able to access whatever content they choose, not the content chosen by the broadband provider.

But it would also allow providers to give preferential treatment to traffic from some content providers, as long as such arrangements are available on "commercially reasonable" terms for all interested content companies. Whether the terms are commercially reasonable would be decided by the FCC on a case-by-case basis.

This latest plan is likely to be viewed as an effort to find a middle ground, as the FCC has been caught between its promise to keep the Internet open and broadband providers' desire to explore new business models in a fast-changing marketplace. It likely won't satisfy everyone, however. Some advocates of an open Internet argue that preferential treatment for some content companies inevitably will result in discriminatory treatment for others.