U.S. new-vehicle sales are on pace to reach the highest March volume since at least 2001, according to three forecasts issued Wednesday, marking a solid start to the closely watched spring selling season.

The forecasts, from LMC Automotive/JD Power, Edmunds and Cox Automotive, project sales to rise about 3 percent this month from March 2017. That would be the industry's largest year-over-year increase since September and the second gain so far in 2018. In contrast, last year started out with eight consecutive months of declines.

"Healthy first-quarter numbers indicate the industry is on solid ground, but that doesn't mean we can expect another banner year for new car sales," Jessica Caldwell, Edmunds' executive director of industry analysis, said in a statement. "Though March tends to be a prognosticator for the year as a whole, if automakers remain disciplined with incentives and further rein in spending, we could potentially see sales start to tumble in the high-volume summer months when shoppers aren't seeing the deals they are looking for."

The LMC/JD Power and Edmunds forecasts call for a seasonally adjusted, annualized selling rate of 16.9 million, which would be the first sub-17 million month since August. Cox has a more conservative estimate of 16.7 million. March 2018 has one more selling day -- and more importantly one additional weekend -- than March 2017.

Automakers are scheduled to report March sales results on Tuesday, April 3.

Analysts said Federal Reserve interest rate increases -- including the most recent hike just this month -- are starting to affect the economy and consumer financing of vehicles, with auto loan rates reaching the highest level since 2013. They said Wall Street volatility and political uncertainty in Washington are discouraging some vehicle buyers, although overall consumer confidence remains high.

"Interest rates are rising as expected, and we are looking for a total of four rate hikes in 2018, a headwind making borrowing more expensive and raising monthly payments," Jeff Schuster, LMC's senior vice president of forecasting, said in a statement.

Cox and LMC said they still expect total sales this year to fall below 17 million, vs. 17.2 million in 2017.

Incentive spending was little changed from a year ago, rising $74 per vehicle to an average of $3,849 in the first 15 selling days of this month, according to JD Power data. Incentives are $160 higher for light trucks but $54 lower on cars.

The industry's average transaction price keeps rising, hitting a March record of $32,129 this month, JD Power said. That's $738, or 2.4 percent, more than the previous record, set just last year.

Light trucks accounted for 66 percent of retail sales so far this month, J.D. Power said, which would be the highest level ever for March. But Cox noted that aggressive discounting by Asian automakers, which are aiming to close out their April-to-March fiscal years strong, could boost cars this month.

Cox said it's also seeing bigger discounts on Ford F-series pickups as it takes on the newly redesigned Ram pickup from FCA US and as General Motors sells down the outgoing version of the Chevrolet Silverado and GMC Sierra to make room for the next generation of its full-size pickups.

Edmunds and Cox are forecasting market-share gains for GM and losses for Ford Motor Co. and Hyundai-Kia. They disagree on their market-share projections for all other major automakers.