MINNEAPOLIS — A Minnesota man with suspected ties to a white supremacist group led by Austin native Samuel Johnson, 31, planned to attack the Mexican consulate in St. Paul to stir debate on immigration amnesty issues ahead of the 2012 election, authorities say.

Joseph Benjamin Thomas, 42, also told an undercover FBI agent he considered himself a “domestic terrorist” instead of an American and would risk his life for the white supremacist movement in the event of a “race war,” the FBI affidavit said. Both Thomas and Johnson were indicted in April.

Thomas, from the St. Paul suburb of Mendota Heights, was indicted on four charges related to possession and sale of methamphetamine, while Johnson was indicted on weapons charges. Johnson pleaded not guilty.

The indictment said Johnson’s prior convictions barred him from having weapons, though he was found with five — including a semi-automatic assault rifle — and more than 1,000 rounds of ammunition.

The document recently unsealed in federal court provides new details about the investigation into Thomas’ alleged plan. It said Thomas amassed weapons and wanted to attack minorities, people with left-leaning political beliefs and government officials. Authorities also accused Johnson in April of amassing weapons and wanting to attack minorities and the government.

Thomas, 42, is not facing any terrorism-related charges. His attorney did not return a phone message Thursday, and the U.S. Attorney’s Office declined to comment.

“We consider him a threat, and we believe he had the capacity to carry these threats out,” FBI spokesman Kyle Loven said Thursday. “This was a lengthy investigation, and it was driven by our belief that the intentions of these persons were sincere.”

In addition to the plot against the consulate, the FBI alleges, Thomas had collected license plate numbers of people with Barack Obama bumper stickers and had asked an associate to volunteer at a left-leaning bookstore to obtain customers’ addresses.

Thomas told an undercover agent he expected a race war within two years and that his group would be able to control an interstate and airports to prevent the military from coming into Minnesota, the affidavit said. In the plot against the consulate, Thomas allegedly told an undercover agent he wanted to steal a pickup truck, load it with barrels of oil and gas, drive it into the consulate and allow the mixture to spill, then set it ablaze with a road flare. Thomas also said he’d found recipes for the mixture and instructions for making napalm, the affidavit said.

The affidavit alleged Thomas wanted to carry out the attack on May 1, a day used in recent years by activists in the U.S. to hold rallies for immigrant rights. But he later said the attack couldn’t happen that day, blaming personal reasons and noting more police were in the area, the affidavit said.

FBI agents reported seeing Thomas conducting surveillance on the consulate building in December. At that point, he told an undercover agent he wasn’t sure if the plot should move forward but continued to develop it and found a place where 55-gallon barrels could be stolen.

Johnson’s trial date has been set for July 16. Thomas’s trial has been set for June 25.

—The Daily Herald contributed to this report.