With the homeland security threat level at the second highest alert — orange — U.S. officials are stepping up security measures throughout the United States.

Streets next to the White House have been closed to the general public. Pedestrian traffic has been eliminated except for visitors attending appointments at the White House complex.

Tourists can no longer have their pictures taken on Pennsylvania Ave., directly in front of the White House, though 200 demonstrators were permitted to stand in Lafayette Park across from the White House Wednesday. About two dozen protesters who tried to climb the fence separating the park from the street were arrested.

Signaling how the orange threat level translates in real life, Homeland Security Secretary Tom Ridge and New York City Mayor Michael Bloomberg met with President Bush Wednesday in the Oval Office to discuss homeland security funding.

After the meeting, Ridge told reporters his top priority.

"The No. 1 mission for everyone engaged in providing homeland security is to prevent the attack from happening in the first place," Ridge said.

In New York City, signs of additional security measures abound. Bridges and tunnels leading into and out of Manhattan show beefed up law enforcement. Police are prowling the city with bomb-sniffing dogs, submachineguns and new technology to detect explosives, chemicals, radiation and bioweapons.

New security measures in New York City alone cost about $5 million per week. Bloomberg is seeking $900 million from the federal government to fund the city's anti-terror effort.

Bloomberg discussed the need for more security funding with the president and said his first concern is the safety of residents.

"New York City, like lots of other cities, has a budget crisis. But first and foremost, we are going to make sure that the people of New York City are as safe as we can possibly make them. And we will worry about the budget afterwards," he said.

Gov. George Pataki sent 202 new state troopers into the field Wednesday, including 120 who will help protect New York's northern border against terrorists. He also met with members of the New York National Guard in Fort Hamilton, Brooklyn, who have been called to active homeland security duty.

Budgeting for the extra security was included in the current fiscal year's spending. The budget for the new fiscal year beginning April 1 is still being negotiated. Pataki proposed a 7 percent increase — to $180 million — for the Office of Public Security.

In other parts of the country, investigators with the FBI and Immigration and Customs Enforcement Bureau continue to interview Iraqis they suspect could be itching to cause trouble.

Authorities are zeroing in on fewer than 100 Iraqis they say could be Saddam Hussein sympathizers. Law enforcement officials acknowledged that the threat level was raised to orange because of the "unfolding events in Iraq and the potential for terrorist attacks carried out against U.S. interests by the government of Saddam Hussein; allied or sympathetic terrorist organizations, most notably the Al Qaeda network; or unaffiliated extremists who oppose U.S. policy."

Law enforcement sources tell Fox News they have a list of about 7,000 people that "might be helpful." Those in violation of immigration laws would be detained, authorities said.

The FBI's weekly bulletin to state and local law enforcement agencies also describes how to identify the license plates of the vehicles of Iraqi diplomatic personnel in New York and Washington, D.C.

The bulletin says Iraqi diplomatic vehicles are distinguished by U.S. Department of State diplomatic license plates with special letter coding identifying the vehicles as belonging to one of the two diplomatic posts. Vehicles attached to Iraq's U.N. Mission in New York City are identified by diplomatic license plates bearing the "TS" letter designation followed by the letter "D'' for diplomat. The letters should follow the license plate number.

Vehicles attached to Iraq's Interests Section in Washington, D.C., are identified by diplomatic license plates bearing the "TF'" letter designation preceded by the letters "D" for diplomat, "S'' for staff or "C'' for consul, following the license plate number.

The FBI says that Iraqi diplomatic vehicles attached to the U.N. mission are required to remain within the "five borough'' area of Manhattan, Queens, Brooklyn, Bronx and Staten Island. Iraqi vehicles attached to the Iraqi Interests Section in Washington, D.C., are required to remain within the 25-mile radius of their Northwest office.

"Suspicious activity involving vehicles bearing Iraqi diplomatic plates should be reported immediately to the nearest Joint Terrorism Task Force,'' the FBI said, saying that diplomatic missions are frequently staffed with members of intelligence services.

On top of the added security, city officials in Washington, D.C., have been sharply criticized for an incident that caused traffic gridlock through five rush hour cycles.

On Wednesday, the standoff that started Monday with an agitated tobacco farmer came to an end. The farmer, identified as 51-year Dwight Watson of Whitakers, N.C., drove his tractor into a pond near the Washington Monument. Watson gave himself up Wednesday afternoon.

Watson, who was protesting cuts in government subsidies to tobacco farmers he said forced him to abandon his trade, claimed to have explosives and that scenario forced D.C. police to shut down traffic through major commuter routes in the center of the tourist area of the city.

Asked for his evaluation of the way law enforcement handled the situation, Ridge said D.C. police erred on the side of caution.

"The first thing it says that we do respect human life, there are obviously all kinds of ways you could have ended that standoff rather quickly, but we chose to do it as we have in other situations, try to get him out without bodily harm to him or the community," he said.

Fox News' Mike Emanuel and Anna Stolley and The Associated Press contributed to this report.