NEWARK, N.J. (AP) _ An ex-Marine who allegedly said he blamed President Reagan for servicemen's deaths in Lebanon was ordered held in lieu of $1 million bail Monday on charges he made verbal threats on Reagan's life, authorities said.

Robert N. Hummel, 26, of Columbia was ordered held at the Metropolitan Correctional Institution in New York City by U.S. Magistrate Robert Cowen after Secret Service officials alleged he made the threats during a conversation in a Washington, D.C., bar.

Hummel will plead innocent, said his attorney, David Gallagher.

Hummel told a bar patron early Wednesday that he had hidden behind bushes as Reagan left Bethesda Naval Hospital in Maryland, where he underwent a physical examination earlier in the month, according to court documents filed by the Secret Service.

Secret Service officials alleged in court papers that Hummel said he was armed with a rifle but was unable to shoot the president because of the presence of Secret Service agents.

The patron contacted the Secret Service, which identified him in court papers as Timothy A. Nero. No age or hometown was given.

Hummel, who is unemployed and lives with his grandmother, was tracked down during a federal computer search that used information he allegedly gave to the bar patron and other people, officials said.

During the conversation with Nero, Hummel ''began talking about the bombing in Lebanon where all the soldiers died,'' and said he ''blamed President Reagan for the heavy loss of lives in Lebanon and proceeded to express his hatred for the president and outlined his plans to kill the president,'' according to the Secret Service court papers.

Hummel told the patron to watch the news during the next few weeks because he was determined to shoot the president, the court papers said.

Hummel ''claimed to have been in the building (the Beruit Marine compound) when it exploded and sustained a leg injury,'' the papers said.

Gallagher said Hummel was in the Marines when the bombing that killed 241 servicemen occurred in Beruit in 1983 but that he did not believe the defendant was ever in Lebanon.

The Secret Service papers said Hummel is appealing the Navy's decision to grant him a 10 percent disability for a knee injury acquired in a motorcycle accident while he was in the service.

And Gallagher said Hummel was in Washington last week for a hearing.

George Hollendersky, special agent in charge of the Secret Service in New Jersey, said Hummel was arrested in the Warren County town of Columbia on Friday and was held at the Bergen County Jail until his hearing.

The magistrate scheduled an April 4 hearing to consider sending Hummel to Washington for further court action.