In a video released Friday, Attorney General Eric Holder announced "a new guide" to help law enforcement officers "maintain public safety while safeguarding constitutional rights during First Amendment-protected events." (Department of Justice)

President Obama and Attorney General Eric H. Holder Jr., in separate media messages Friday, urged protesters in Ferguson, Mo., to avoid violence as the nation awaits a grand jury’s decision in the Michael Brown case.

Holder also expressed concerns privately about Gov. Jay Nixon’s decision this week to declare a state of emergency at a news conference and activate the National Guard. The grand jury decision in the Ferguson shooting is expected to be announced in the next few days.

In an interview Friday with ABC News, Obama said Americans have a right to express their views, but not use that right “as an excuse for violence.”

“I think first and foremost, keep protests peaceful,” Obama said in the interview, which was taped after his speech in Las Vegas kicking off his campaign to rally support for his executive action on immigration.

“This is a country that allows everybody to express their views, allows them to peacefully assemble, to protest actions that they think are unjust,” Obama said, according to the Associated Press. “But using any event as an excuse for violence is contrary to rule of law, contrary to who we are.”

A top aide to Holder called the governor’s office earlier this week to express Holder’s displeasure and “frustration,” according to a Justice Department official.

“Instead of de-escalating the situation, the governor escalated it,” said the official, who spoke on the condition of anonymity because he was not authorized to speak on the subject. “He sent the wrong message. The tone of the press conference was counterproductive.”

A spokesman for Nixon (D) declined to comment.

Senior Justice officials also told U.S. attorneys around the country on Tuesday to be in close touch with local police to prepare for any possible violence in their cities, should the grand jury decision not result in an indictment of Ferguson police officer Darren Wilson for the fatal shooting of Brown, an unarmed black teenager, on Aug. 9.

On Friday, Holder released a video, reminding potential demonstrators that “history shows that most successful movements adhere to nonviolence.”

“I ask all those who seek to lend their voice to important causes and discussions, and who seek to elevate these vital conversations, to do so in a way that respects the gravity of their subject matter,” Holder said in the video. “Peaceful protest has been a hallmark, and a legacy, of past movements for change, from patriotic women who demanded access to the franchise, to the civil rights pioneers who marched for equal rights and equal justice.”

In the video, Holder expresses sympathy with the protesters — although he did not use the word “Ferguson.”

“Of course, I recognize that progress will not come easily, and long-simmering tensions will not be cooled overnight,” Holder said. “These struggles go to the heart of who we are, and who we aspire to be, both as a nation and as a people — and it is clear that we have a great deal of important work still to do.”

St. Louis remained on edge Friday .

“The city is in a panic at this point ahead of the announcement,” said Brown family attorney Anthony Gray, who called a news conference to reiterate the family’s calls for peace. “They do not advocate violence, looting, riots.”

The county prosecutor’s office confirmed Friday that the grand jury continued to meet, while state officials, attorneys for both Wilson and the Brown family, and community leaders signaled that they think an announcement was likely to come over the weekend.

Meanwhile, the Jennings School District, one of several districts that serves students from Ferguson, announced it was canceling classes Monday and Tuesday.

Protests outside the Ferguson Police Department — which have continued daily since the Aug. 9 shooting — have turned the most tense they have been in close to a month. Slay and St. Louis County Executive Charlie Dooley said Friday that officers will prioritize life, property and speech rights.

“To the demonstrators who want to be heard, we hear you, we are listening and we will continue to protect your right to speech,” Dooley said. “To the property owners who have been worried and anxious in the last two weeks and who have been hoping and wanting to be safe, we are going to protect your businesses.”

Along with Holder’s call to U.S. attorneys this week, the FBI issued a nationwide law-enforcement bulletin warning that the grand jury’s decision “will likely” lead to attacks on police officers or federal agents.

The Justice Department has two ongoing investigations in Ferguson in connection with the shooting of Brown. One is a civil rights investigation into the shooting, which is not expected to result in charges. The other is a broad investigation of the policing practices of the Ferguson Police Department, which could result in wholesale reforms and a reorganization of the department.

Wilson is unlikely to return to his job regardless of whether a grand jury decides to indict him, Ferguson Police Chief Thomas Jackson said Thursday.

“I don’t see it happening,” Jackson said in a brief interview.