FILE PHOTO: U.S. Senate Judiciary Committee Chairman Senator Chuck Grassley (R-IA) speaks during a news conference to discuss the FBI background investigation into the assault allegations against U.S. Supreme Court nominee Judge Brett Kavanaugh on Capitol Hill in Washington, U.S., October 4, 2018. REUTERS/Yuri Gripas/File Photo

WASHINGTON (Reuters) - Republican Senator Chuck Grassley said on Tuesday that the U.S. Environmental Protection Agency must act quickly to allow year-round sales of higher ethanol gasoline blends if President Donald Trump aims to keep a campaign promise to corn farmers.

Trump announced during a trip to Iowa this month his intention to lift the summertime ban on sales of so-called E15 gasoline to help corn growers stung by slumping prices.

The EPA has since said it will finish deliberations on a proposal to lift the ban by May, a timeline the administration hopes will put the rule in place before summer. But Grassley said that was too slow.

“EPA ought to speed it up. Otherwise it is going to look like the President wasn’t serious in his announcement,” he told a weekly conference call.

“We don’t need a lot of bureaucratic red tape with something that has been discussed in Washington for four to five years, and discussed... specifically with EPA and face-to-face with the President for about a year,” he said.

Trump’s announcement encouraged farmers eager to expand the market for corn-based ethanol, and was seen as a political victory for Trump ahead of congressional elections in November.

The EPA’s ban on summer E15 sales was initially intended to reduce smog, but academic studies have concluded that the ban is ineffective at improving air quality.

Trump’s move, however, is likely to face pushback from the oil industry, which has long opposed the rule change since it would cut into its share of the petroleum market. The industry has threatened to sue over the issue.

Some industry experts say the administration will ultimately need an act of the Congress to change the rule. EPA acting chief Andrew Wheeler, however, rejected that idea earlier this month, saying the agency has the authority to move ahead alone.