WASHINGTON (Reuters) - The leaders of the U.S. intelligence community on Thursday pressed Congress to renew the National Security Agency’s expiring surveillance law, warning in a rare public statement that national security may be endangered if lawmakers let it lapse.

The message from the intelligence chiefs sought to apply pressure on lawmakers who appeared to abandon an effort this week to pass legislation that would have reauthorized for several years the NSA’s warrantless internet spying program, which is due to expire on Dec. 31.

That plan cratered late on Wednesday amid objections from a sizable coalition of Republicans and Democrats who want to have more privacy safeguards in the program, which chiefly targets foreigners but also collects communications from an unknown number of Americans. Instead, House Republicans unveiled a stopgap funding measure on Thursday that includes an extension of the surveillance law until Jan. 19.

The law, known as Section 702 of the Foreign Intelligence Surveillance Act, is considered by U.S. intelligence agencies to be vital to national security.

“There is no substitute for Section 702,” Director of National Intelligence Dan Coats, Attorney General Jeff Sessions, and the directors the NSA, FBI and CIA wrote in the joint statement, adding that failure to renew the authority would make it easier for foreign adversaries to “plan attacks against our citizens and allies without detection.”

Section 702 allows the NSA to collect vast amounts of digital communications from foreign suspects living outside the United States. But the program incidentally gathers communications of Americans for a variety of technical reasons, including if they communicate with a foreign target living overseas.

Those communications can then be subject to searches without a warrant, including by the Federal Bureau of Investigation. Some lawmakers in both parties want to eliminate or partially restrict the U.S. government’s ability to review data of Americans collected under Section 702 without first obtaining a warrant.

The intelligence chiefs also criticized the current plan to temporarily extend the program, saying short-term extensions “fail to provide certainty and will create needless and wasteful operational complications.”

U.S. officials recently acknowledged the end-year deadline may not matter much because of a belief the program can lawfully continue through April due to the way it is annually certified.

In their statement, however, the intelligence chiefs warned that the surveillance program would need to begin “winding down” well in advance of the April date.