PITTSBURGH - Shackled to a wheelchair, the man accused of fatally shooting 11 worshipers at a Pittsburgh synagogue made a stony-faced, largely silent appearance on Monday in a federal courtroom, where he was ordered held without bond in the deadliest attack ever on America's Jewish community.

The arraignment of accused gunman Robert Bowers came as the White House said US President Donald Trump would visit Pittsburgh on Tuesday to pay respects to the victims, a move opposed by the mayor and some of the city's Jewish leaders.

Bowers, 46, wounded in a gunfight with police on Saturday at the Tree of Life synagogue before his arrest, acknowledged the 29 felony counts against him, including charges of violating US civil rights laws in what federal prosecutors are treating as a hate crime.

If convicted, he could face the death penalty.

A judge ordered Bowers, a onetime truck driver known to frequently post anti-Semitic material online and described by neighbors as a loner, to remain in federal custody and be assigned a defense attorney by the court. His next hearing was set for Thursday.

The synagogue massacre has heightened debate over the inflammatory rhetoric used by Trump, with critics, including Pittsburgh Mayor Bill Peduto, saying it had fostered a climate of political hostility and encouraged right-wing extremism.

"Yes, words matter," Peduto, a Democrat, said during a CNN interview on Monday. He also said he believed Trump should wait until all the funerals were held before coming to Pittsburgh.

The president and first lady planned to travel on Tuesday to Pennsylvania to "express the support of the American people and grieve with the Pittsburgh community," White House press secretary Sarah Sanders said at a briefing.

Over the weekend, Trump branded Saturday's shooting an act of pure evil but also told reporters the slaying might have been prevented had an armed guard been present at the synagogue.

The Trump administration has rejected the notion he has encouraged white nationalists and neo-Nazis who have embraced him. But a group of local Jewish leaders told Trump in an open letter on Monday he was "not welcome in Pittsburgh until you fully denounce white nationalism."

More than 27,000 people have signed the letter, organized and posted online by the Pittsburgh chapter of Bend the Arc, a Jewish organization focused on opposing "the immoral agenda of the Trump administration and the Republican Party."

Tree of Life Rabbi Jeffrey Myers, said, however, on ABC on Monday that the president of the United States was always welcome to visit.