The nation's Homeland Security chief pushed back Thursday against Republican threats to cut off funding for the department to protest President Obama's immigration policies.
The department's budget runs out at the end of February, and Republicans have threatened to hold up additional appropriations unless the Obama administration pulls back plans to stop the deportation of up to 4 million immigrants who are in the country illegally.
"In these times, the Homeland Security budget of this country should not be a political football," Jeh Johnson, the secretary of Homeland Security, said at the Wilson Center, a think tank in Washington.
The United States faces increased threats from terrorist groups, Johnson said, particularly in the wake of the three-day killing spree that left 17 people dead in Paris this month. An Al Qaeda offshoot in Yemen claimed responsibility.
To press his point, Johnson showed the audience a photo of himself as an 8-year-old boy with his family next to their Buick convertible. It was parked a few feet from the U.S. Capitol during a sightseeing visit in 1966.
That would not be allowed today, Johnson said.
"Sadly, there are threats to our homeland security today that did not exist in 1966," Johnson said. "We have to be vigilant."
Johnson said that his agency and the FBI do a "reasonably good job" of tracking Westerners who have joined the civil war in Syria, or the insurgency in Iraq, and may try to return home to launch attacks.
Europe faces a greater immediate danger, Johnson said, because thousands of French, British, German, Dutch and other citizens have traveled to Syria, compared with about 100 Americans.
"They have much bigger numbers," he said.
Johnson said his department is reviewing security measures to screen travelers, mostly from countries in Europe, who don't require visas to enter the United States.
U.S. lawmakers have asked the administration to further restrict the so-called visa waiver program to help prevent fighters with European passports from crossing a U.S. border.
Earlier this month, Sen. Dianne Feinstein (D-Calif.) described the visa waiver program as the "Achilles' heel of America."
Passengers from visa waiver countries need not be interviewed by an American consular officer. They instead fill out an online information form before boarding a U.S.-bound flight.
The information is checked against U.S. databases for ties to terrorist groups or suspicious travel patterns. Last year, the U.S. increased the amount of information such travelers must provide.
Three former secretaries of Homeland Security also spoke out Thursday about threats by Congress to shut down funding for the department.
Tom Ridge, Michael Chertoff and Janet Napolitano sent a joint letter to Senate leaders asking them not to link Homeland Security funding with the effort to stop Obama's immigration actions.
"Funding for the entire agency should not be put in jeopardy by the debate about immigration," the three wrote in the letter to Senate Majority Leader Mitch McConnell (R-Ky.) and Minority Leader Harry Reid (D-Nev.).
Ridge and Chertoff served in the Republican administration of President George W. Bush. Napolitano, a Democrat, headed the department during Obama's first term.
Obama has said he would veto a spending bill that stripped funding for his new executive actions on immigration.
In addition to enforcing immigration and customs laws, the Homeland Security Department is responsible for aviation and border security, protecting the president and responding to natural disasters.