Federal and local officials ramped up precautionary measures in preparation for three days of memorial observances for former president Ronald Reagan, granting employees additional leave today in hopes of avoiding major traffic and security problems.

Federal employees will be allowed to take unscheduled leave today, meaning the time off does not need prior approval. Most D.C. government employees may request liberal leave beginning at 2 p.m.

The impetus for the moves, officials said, was word that police plan to close Constitution Avenue and all cross streets between 23rd Street NW and the U.S. Capitol from 3 to 9 p.m. The closings also will affect the 12th and Ninth Street tunnels, officials said.

Reagan's coffin is due at Andrews Air Force Base at 5 p.m. today and will reach the Capitol about two hours later, officials said. Public viewing will begin at 9 p.m. and last until 7 a.m. Friday.

"It's like putting a giant canal through the city," Tony Bullock, spokesman for D.C. Mayor Anthony A. Williams (D), said of the street closings. "If you are on one side, you'll have a hell of a time getting to the other side. Getting them out earlier in the day could make a big difference."

Williams also announced that D.C. government offices and public schools will be closed Friday, along with federal offices.

Also yesterday, final preparations were underway for Reagan's state funeral.

Military jets streaked in formation across the sky. A riderless horse paced in front of the Capitol steps while a military band played and tourists' cameras clicked. Landscapers hurriedly planted rows of red and yellow flowers. Police and Secret Service officers began roping off streets, sidewalks and entranceways at federal buildings and hotels.

Last night, part of Constitution Avenue NW was shut down for a rehearsal of today's procession that will take Reagan's coffin to the Capitol. First, six horses drew a caisson part way along the avenue's 1600 block; then, members of the armed forces removed a flag-draped coffin from a hearse and placed it on the caisson.

In Simi Valley, Calif., more than 50,000 people passed through the Ronald Reagan Presidential Library in 24 hours to view Reagan's flag-draped coffin, according to an estimate. Viewing was extended until 10 last night.

On Capitol Hill, federal lawmakers remarked on the former president's contribution. "The world is a better place because of President Reagan's leadership. That legacy gives him a special place in history," said Sen. Arlen Specter (R-Pa.).

While many D.C. residents and tourists applauded the grand proceedings, others wondered whether the hoopla was too much.

"They're giving him too much play," said Johnnie J. Wallace, a Washington chef. "Look how much it's costing taxpayers. People are losing money. The media are doing too much. You turn on the TV and what do you hear? What about the war in Iraq?"

Closing the federal and District governments Friday will result in a significant loss of productivity. The Office of Personnel Management has estimated the loss from a one-day closure of federal operations in the Washington area, such as during a snow emergency, at $66 million. But many operations that would be closed for snow will operate as usual, including agencies of the State, Defense, Justice and Homeland Security departments.

A House official gave a rough estimate of $1.5 million for the Capitol's share of this week's ceremonies. The official said the Ronald Reagan Memorial Foundation was expected to pick up two-thirds of the cost and that congressional agencies would absorb the rest.

Natwar M. Gandhi, the District's chief financial officer, estimated local police, transportation and public works costs at $500,000 and said the city would seek federal reimbursement. The District planned to offer water and medical aid to people attending events today, when temperatures could reach into the 90s.

Outside the Capitol yesterday, men in uniform representing each of the armed services carried an empty coffin draped in an American flag during a dress rehearsal.

Groups of tourists in shorts and T-shirts milled about and snapped pictures as they might on any day -- only this time, some sensed that their memories of this day would not soon fade.

"Reagan was an awesome president, and it's just historic to be here," said Deborah Rocchild, 35, of San Francisco, who was visiting with her husband, Oscar, and their son, Christian, 6.

Daniel Delorimier, 14, who was in a group of boys from a Catholic school in Salinas, Calif., said his parents had told him that Reagan had been a "great president."

"I was excited because he will only [lie] in state for three days and this is a once-in-a-lifetime chance," Daniel said.

Meanwhile, more foreign dignitaries confirmed they will attend Friday's funeral at Washington National Cathedral, including South African President Thabo Mbeki and Canada's head of state, Governor General Adrienne Clarkson, according to officials. The Vatican also announced that its secretary of state, Cardinal Angelo Sodano, would represent Pope John Paul II. Lech Walesa, Poland's former president and founder of the Solidarity trade union, also said he would attend the funeral, according to a wire service report.

And former president Gerald R. Ford, whose presence was in doubt for health reasons, will attend, said Penny Circle, his chief of staff.

Transportation officials braced for backups that were expected to start this afternoon. D.C. police announced that the motorcade carrying the former president's body would start into the city on Suitland Parkway to avoid rush-hour traffic on the Capital Beltway.

Officials nevertheless advised drivers to use Route 301 or the western arc of the Beltway to avoid the Andrews area. Transportation officials added highway crews, posted signs alerting drivers to road closures and pleaded for people to take mass transit.

Lon Anderson, a spokesman for AAA, said: "There will be enormous disruption downtown. . . . But I think traffic will be all right because the federal government has given plenty of warning."

Downtown hotel managers said they expect most guests attending Reagan funeral events to check in today or tomorrow.

Miami Beach business consultant Anthony Ferrari, his wife, Jessie, their young daughter and a five-car entourage of aides already were encamped at the Madison Hotel yesterday. Ferrari hoped to see the horse-drawn procession to the Capitol tonight and perhaps see Reagan's coffin in the Capitol Rotunda tomorrow.

"I'm a big fan of President Reagan," he said. "I met him once. . . . The man had a big impact on America. He really loved this country and it showed."

Staff writers Charles Babington, Karlyn Barker, Stephen Barr, Steven Ginsberg, Avram Goldstein, Sari Horwitz, Allan Lengel, Caryle Murphy, Lena H. Sun, Martin Weil and Clarence Williams and the Associated Press contributed to this report.