Connecticut Governor Dannel Malloy called for residents of his state to observe the moment at 9:30 am EST (1430 GMT) to mark a week since a 20-year-old gunman killed his mother and then stormed Sandy Hook Elementary School in Newtown, where he shot to death 20 children and six adults before killing himself.
Malloy's fellow governors in Maine, Illinois, Michigan and several other states called on residents to follow suit with a moment of silence and to ring bells to remember the dead. The National Cathedral in Washington plans to ring its bell 28 times as part of an interfaith memorial.
"We have the moral obligation to stand for and with the victims of gun violence and to work to end it," said Reverend Gary Hall, dean of Washington National Cathedral, who called on Americans to pray "that we may have courage to act, so that the murderous violence done on Friday may never be repeated."
The company that operates the Nasdaq stock exchange said its operations would observe a moment of silence at 9:30 am, although market will open trading at that time as usual.
The observances will be held not long before the National Rifle Association, the largest U.S. gun rights group and one with powerful ties to Washington politicians, begins a media campaign to become part of the gun control debate prompted by the stunning slaughter of 20 children, all 6 or 7 years old.
Laws restricting gun ownership are controversial in the United States, a nation with a strong culture of individual gun ownership. Hundreds of millions of weapons are in private hands.
\About 11,100 Americans died in gun-related killings in 2011, not including suicides, according to preliminary data from the U.S. Centers for Disease Control and Prevention.
he NRA remained quiet for four days after the Newtown slaughter, citing "common decency." It released a short statement on Tuesday saying it was "prepared to offer meaningful contributions to help make sure this never happens again."
The group scheduled a news conference for 10:45 am (1545 GMT) on Friday in Washington. NRA chief executive Wayne LaPierre planned to appear on the NBC television talk show "Meet the Press" on Sunday.
Some U.S. lawmakers called for swift passage of an assault weapons ban.
Vice President Joe Biden convened a new White House task force on Thursday charged by President Barack Obama with finding ways to quell violence.
"We have to have a comprehensive way in which to respond to the mass murder of our children that we saw in Connecticut," Biden told the group, which included Attorney General Eric Holder, Thomas Nee, president of the National Association of Police Organizations, and other officials.
The gunman, Adam Lanza, used a military-style assault rifle and police said he carried hundreds of bullets in high-capacity magazines, as well as two handguns. The weapons were legally purchased and registered to his mother, Nancy, his first victim.
By Thursday, funeral services had been held for more than half of the 27 people Lanza killed last week.
Newtown school officials said that Friday would be a shortened day for students heading into the Christmas break.
Reflecting a heightened state of alert at schools across the United States, a school district near Boise, Idaho, canceled planned assemblies at a number of its 50 schools after receiving a rash of threats that suggested "something bad" would happen on Friday, Meridian school spokesman Eric Exline said.
"The event last Friday in Connecticut has unnerved people in a lot of ways," he said.
The New Milford school district, near Newtown, canceled Friday classes "on the advice of the New Milford Police Department" but did not offer any further explanation.
In Florida, a 13-year-old student was arrested on Thursday after he allegedly posted a Facebook message threatening to "bring a gun to school tomorrow and shoot everyone," said the St. Lucie County Sheriff's office on Florida's east coast.
Police said the teen did not have any weapons and posed no threat to local schools. He was charged with making a written threat and is being held at a local Juvenile Detention Center.