PORTLAND, Ore. — Supporters of an Oregon-only plan to replace the Interstate 5 bridge across the Columbia River hope to put the issue in front of the Legislature again as early as this month.

The project is in doubt because it was supposed to be a joint effort of Oregon and Washington state, but the Washington Legislature didn’t put up $450 million to match Oregon’s contribution to a project now estimated to cost $2.7 billion.

Supporters, including business and labor groups say a new bridge is still critical, The Oregonian reported Monday.

The project faces a variety of skeptics, among them some conservatives, Washington opponents of light-rail trains and environmentalists.

The Oregon-led plan relies on $1.3 billion worth of tolls. An $850 million federal grant would extend light rail from North Portland to Vancouver.

A state analysis says the project would pencil out if interest rates stayed relatively stable and if the federal government approved a $900 million loan to Oregon providing cash as tolls rolled in over the next 35 years.

“It is all doable, but it is very much threading a needle to make it all come together,” said Laura Lockwood-McCall, director of debt management in the state treasurer’s office.

If something went awry after the project broke ground, the state could have to fill the gap with general obligation bonds or other state funds — a mind-changer for lawmakers such as Republican Rep. Dennis Richardson of Central Point who voted for the bridge earlier this year.

Washington agencies would still play a role.

The Oregon Department of Transportation would need agreements with its Washington counterpart to oversee construction. During construction Oregon would collect tolls on the existing Interstate 5 bridge. Tolls are expected to range between $1.50 and $4.00 each way, depending on time of day.

Oregon would set the rate. But Washington officials would have to enforce the tolls by punishing Washington drivers who refuse to pay.