President Donald Trump will meet on Sept 19 with U.S. senators to discuss biofuels policy, Senator Bill Cassidy's office said, as Trump attempts to find a compromise between the oil and gas industry and the corn industry on an issue that pits two constituencies that are important to Trump's quest for a second term against each other.

The meeting will continue a marathon of discussions the White House has held since last week with biofuel and oil refining advocates—including senators from key farm states and refining executives--to negotiate a deal over how much ethanol should be blended into the nation's gasoline. Thursday's meeting will likely focus on the demands of the oil industry.

Trump had promised a package related to corn-based ethanol after his administration's decision in August to exempt 31 oil refineries from their blending requirements caused outrage in the Farm Belt.

Following last week's meetings, Trump tentatively approved a plan to increase the amount of biofuels that refiners are required to blend each year under the Renewable Fuel Standard, to compensate for the exemptions, two sources familiar with the matter said. That plan is likely to upset the oil industry, which argues that increased blending requirements would put blue-collar refinery jobs at risk.

Trump has inserted himself into the negotiations between the rival oil and corn industries to try to appease both groups, which helped win him the presidency in 2016 and could play a key role in his 2020 re-election bid.

Under the RFS, oil refineries must use billions of gallons of biofuels like ethanol--a regulation intended to help farmers and cut U.S. petroleum imports. Small facilities of 75,000 barrels per day or less can secure waivers if they prove complying with the regulation would cause them disproportionate financial hardship.

Corn farmers and ethanol producers say the Trump administration's broad use of the exemption program undermines demand for ethanol at a time the industry is already suffering from a loss of foreign markets due to the U.S. trade war with China. But the oil industry says the exemptions help ensure that small refiners stay in business.

Cassidy's office said in the statement announcing Thursday's meeting that increasing the amount of renewable fuel required to be blended into gasoline will increase costs for refiners in Louisiana, the state that Cassidy represents in the Senate.

"Refineries employ thousands of energy workers in Louisiana, and increasing their compliance costs will put jobs in jeopardy," Cassidy said in the statement.

On Wednesday, Senator Chuck Grassley of Iowa, an important farm state, said he supported Trump's p