An influential bipartisan pair of senators unveiled a climate change measure Friday that is intended as an alternative to “cap-and-trade” legislation, potentially complicating the dynamics of passing a global warming bill in the Senate.

Democrat Maria Cantwell of Washington and Republican Susan Collins of Maine are among a group of moderate lawmakers from both parties who like the idea of capping carbon emissions but oppose creating a new financial market for trading emissions permits.

The “cap and trade” model is the centerpiece of the House-passed climate bill (HR 2454, as well as a compromise Senate bill that Massachusetts Democrat John Kerry , Connecticut independent Joseph I. Lieberman and South Carolina Republican Lindsey Graham are assembling.

But Cantwell, Collins, and a small but growing number of other lawmakers — whose votes may be crucial to passing a climate bill in the Senate — say they are haunted by the nightmare of last year’s financial markets collapse. They fear a cap-and-trade system would create a new commodity market ripe for speculation that could cause volatile price spikes that would harm consumers and the economy.

The Cantwell-Collins alternative would instead create what has been called a “cap and dividend” structure. The government would still cap emissions and sell carbon permits, but the polluters — such as coal producers and oil companies — could trade the credits only among themselves. There would be no outside market for trading the emissions credits.

Under the Cantwell-Collins plan, 75 percent of the revenue raised by selling emissions permits would go straight back to U.S. taxpayers in the form of monthly electronic payments made directly to their bank accounts. Cantwell’s office is expected to release a report Friday finding that under the plan, a typical family of four would receive tax-free monthly checks from the government averaging $1,100 per year, or $21,000 between 2012 and 2030.

The remaining 25 percent would be spent on projects such as clean energy technology research and development.

That approach has appeal to moderate Democrats such as Byron L. Dorgan of North Dakota, who has said that he will vote against any bill that creates a new carbon market, and Jim Webb of Virginia, who has said he is uncomfortable with the idea of creating a new financial commodity.

Collins’ backing of the measure is also significant.

Democrats putting together the broader cap-and-trade climate bill have said they assume they will lose a handful of votes from their party and will need the support of moderate Republicans like Collins and her Maine colleague Olympia J. Snowe in order to move it through. But Collins last week called the House-passed bill a “monstrosity.”

That could complicate things for Kerry, Lieberman and Graham, as well as for U.S. negotiators in at the U.N. climate summit in Copenhagen, who hope to show that senators are coalescing around a broad, bipartisan climate effort.

Although their proposal is fundamentally different from the Kerry-Lieberman-Graham effort, Cantwell and Collins said they hope to work with the trio and the White House and expect introduction of their bill resonate positively in Copenhagen.

“The president has taken our shared emission-reduction goals to the Copenhagen conference and the response there underscores global interest tackling the problem,” Cantwell said. “It also shows that there will be a highly competitive international business environment for leadership in clean-energy technology.”