CONNECTICUT GOV. Ned Lamont on Tuesday said he is putting on hold his pursuit of the Transportation Climate Initiative, leaving Massachusetts in a precarious, go-it-alone position as the regional cap-and-trade gasoline initiative is scheduled to begin practice runs next year and launch formally in 2023.

According to news reports in Connecticut, Lamont said he couldn’t overcome opposition to the initiative in the legislature when gas prices were at historic lows low so there was no way he was going to continue pushing for it when prices are at a seven-year high and he and lawmakers are up for reelection next year.

“It’s probably not the year to do it this year with gas prices where they are,’’ Lamont said.

Asked whether the proposal could be revived in 2023, Lamont said, “Yeah, let’s see where we are.”

Massachusetts, Connecticut, Rhode Island, and the District of Columbia signed on to the Transportation Climate Initiative last December, agreeing to put a price on the carbon contained in vehicle fuels sold within their borders and leverage the revenues gained and the resulting higher price of gasoline to cut transportation emissions 26 percent by 2032.

The number of states participating in the initiative was far smaller than what Gov. Charlie Baker had hoped for, but his administration said Massachusetts, Connecticut, and Rhode Island were the key participants and other states might sign on later. Baker and his aides said the three southern New England states account for 73 percent of total emissions in New England, 76 percent of vehicles, and 70 to 80 percent of the region’s gross domestic product.

Lamont has been unable to get the Transportation and Climate Initiative through the Connecticut legislature and Rhode Island hasn’t adopted it yet, either. In Massachusetts, Baker says he can sign on to the initiative under authority granted to him under existing law.

The Transportation Climate Initiative calls for fuel wholesalers to purchase at auction allowances permitting them to sell gasoline in Massachusetts and the other participating states. The number of allowances will be reduced every year, driving up the price of gasoline. Under the memorandum of understanding the states issued last December, wholesalers would begin a walk-through of the process in 2022 and begin paying for the allowances in 2023.

Katie Theoharides, the secretary of energy and environmental affairs, said Massachusetts needed a program like the transportation climate initiative if it was going to have a chance of reaching its goal of net zero emissions in the state by 2050. “We can’t get there without a program like this,” she said.