A Seattle-area man appeared in federal court on Wednesday (local time) on charges of threatening to assassinate US President Barack Obama in a taunting email to the FBI and assaulting a federal agent sent to arrest him.

Anton Caluori, 31, was arrested at his apartment south of Seattle on Tuesday after the FBI notified the Secret Service about the alleged threat.

He had five guns, including two assault rifles, when arrested, according to the criminal complaint against him.

"I will kill the president!" Caluori wrote in a profanity-laden email, according to the complaint. "Come get me."

"You have 7 days ... Get me to Alcatraz now," he wrote, referring to the now-closed island prison in the San Francisco Bay. "You can't afford to call my bluff.".

Clean-shaven and wearing prison clothes, Caluori seemed alert during the hearing on Wednesday in US District Court for the Western District of Washington in Seattle.

His court-appointed attorney requested a mental evaluation of her client.

He was also accused of pointing a gun at a Secret Service agent who was with a local police officer during the arrest.

The charges against him carry a combined maximum sentence of 25 years in prison.

Defence attorney Kyana Stephens declined to speak to reporters after the hearing.

When asked if Caluori represented a threat to Obama, Assistant US Attorney Steven Masada told reporters: "We take all threats against the president seriously."

Masada said Caluori appeared to have been discharged from the Navy within the last 10 years.

Magistrate Judge James Donahue scheduled a hearing for Monday to discuss the request for a mental health evaluation and to consider the terms of Caluori's detention, including the possibility of bail.

- Reuters