WASHINGTON — House Democrats are considering an insurance tax to help pay for their health care overhaul plan, even though such a funding scheme is opposed by labor unions that are among the party's most loyal constituencies.

House Speaker Nancy Pelosi, D-Calif., said today a tax on high-cost health insurance plans is "under consideration" as Democrats search for consensus within their ranks before taking a bill to the House floor later this fall.

She didn't specify what other provisions she might find more acceptable. An aide said that if the House does incorporate an insurance tax in its plan, it would probably be a more modest one than what Senate Finance Chairman Max Baucus, D-Mont., proposed.

The House Democratic plan calls for raising income taxes on upper-income people to pay for covering the uninsured. Baucus has instead proposed a tax on high-cost insurance plans worth more than $8,000 for an individual policy and $21,000 for family coverage.

Proponents of the insurance tax, which President Barack Obama has endorsed, say it would help to lower health care costs by encouraging people to become more cost-conscious health care consumers.