Federal prosecutors told jurors Monday that alleged Benghazi mastermind Ahmed Abu Khattala “hates America with a vengeance,” as the long-awaited trial began for the only suspect held in connection with the 2012 attack.

Both sides delivered opening statements at a Washington federal courthouse.

Khattala faces 18 federal charges, including murder. Four Americans were killed in the Sept. 11, 2012, attack: Ambassador Christopher Stevens, State Department official Sean Smith and security officers Tyrone Woods and Glen Doherty, both former Navy SEALs.

“Ambassador Christopher Stevens was choked to death by thick black smoke. … Glen Doherty was blown apart by a mortar attack. Why? Because they were Americans. And that defendant, right there, hates America with a vengeance,” Assistant U.S. Attorney John Crabb said while motioning at Khattala, dressed in a white shirt and sitting expressionless at the defense table.

'Ambassador Christopher Stevens was choked to death by thick black smoke. … Glen Doherty was blown apart by a mortar attack. Why? Because they were Americans.' — Prosecutor John Crabb

Crabb, in the prosecution’s 60-plus minute opening statement, said Khattala believed the State Department compound, where Stevens and Smith died, and the nearby CIA annex were U.S. spy operations. Both posts came under attack.

“And that concern and that desire drove Abu Khattala to kill,” Crabb said.

Defense lawyers, in their opening statement, argued they have evidence that will show Khattala is not guilty and was not the so-called mastermind behind the attacks.

They said their client was, in fact, someone the United States and Libya decided could be readily blamed.

“He was a soft target,” defense attorney Jeffrey Robinson said, calling Khatalla a “Libyan patriot.” “He didn’t have anything to do with it. That’s why he talked to reporters and answered questions about it. He wasn’t in hiding from anything.”

Stevens and Smith died at the compound from the smoke of a fire started by the attackers, whom Crabb said were associates of Khattala.

Tyrone Woods and Glen Doherty died nearly eight hours later at the CIA annex during the mortar attack.

Crabb showed a video that appeared to show Khattala outside the State compound during the first attack, then entering after the Americans left so he could ransack a room in which top-secret U.S. documents including maps were kept.

“Abu Khattala didn't do the killings by himself. He didn’t set the fire. He didn’t fire the mortar,” Crabb said. "But Abu Khattala planned the attack. ... He got others to do his dirty work."

The defense team said Khattala went to the State Department compound to see what was going on and never stopped anyone from trying to rescue the Americans.

“He didn't attack or shoot anyone, nor go to the CIA annex. … They have no evidence,” said the defense lawyer, further arguing government witnesses are in fact political enemies of Khattala.

The 2012 attack became instant political fodder, with Republicans accusing the Obama administration of intentionally misleading the public and stonewalling congressional investigators, though officials denied wrongdoing.

It continued to be a problem for Hillary Clinton during her failed 2016 White House bid, as critics accused her of pushing a false narrative linking the attack to protests over an anti-Islam video -- and her State Department of neglecting security needs of the team on the ground before the attack.

The case is one of the most significant terrorism prosecutions in recent years in a U.S. civilian court. It comes at a time when the Trump administration has said terror suspects are better sent to the military prison at Guantanamo Bay, Cuba.

Khattala has pleaded not guilty to the charges, which also include providing material support to terrorists and destroying U.S. property while causing death.

Khattala, who has a long, gray beard, entered the courtroom and shook hands with members of his legal team.

Before the opening statements, U.S. District Judge Christopher Cooper gave the jury 30 minutes of instructions.

"This is a criminal case,” he told the 15 jurors, including three alternates. "You and only you are the ultimate deciders of fact in this case."

Khattala was captured three years ago by U.S. Special Forces in Libya and brought to the U.S. on a 13-day trip aboard a Navy ship.

The defendant’s lawyers have argued U.S. interrogation strategies on the trip were illegal. During his trans-Atlantic trip, Khattala faced days of questioning from separate teams of American interrogators, part of a two-step process designed to obtain both national security intelligence and evidence usable in a criminal prosecution.

He was questioned for days about national security matters before being advised of his rights. A new team of FBI investigators then pressed him some more, this time to produce evidence prosecutors could present at trial.

Abu Khattala waived his rights, but his attorneys argued that the trip was so coercive, the waiver shouldn't count.

The judge rejected that, and is allowing the statements to be used as evidence.

Fox News' Jason Donner and The Associated Press contributed to this report.