WASHINGTON  With Congress at an impasse over the government’s spy powers, Congressional and intelligence officials are bracing for the possibility that the government might have to revert to the old rules of terrorist surveillance, a situation that some officials predict could leave worrisome gaps in intelligence.

That prospect seemed almost inconceivable just a few months ago, when Congressional negotiators and the White House promised a quick resolution to a bruising debate over the government’s surveillance powers. But the dispute has dragged on. Though both sides say they are hopeful of reaching a deal, officials have been preparing classified briefings for Congress on the intelligence “degradation” they say could occur if there is no deal in place by August.

The deadline is considered critical because of a series of secret one-year wiretapping orders that were approved last August under a controversial temporary wiretapping law. The law allowed the National Security Agency to use blanket court orders to focus on groups of suspected Qaeda terrorists based overseas. But those orders are growing staler by the day, officials said, and will begin to expire this August if nothing is done. (Wiretaps intended for Americans already require individual warrants issued by a secret court, known as the Foreign Intelligence Surveillance Act court, or FISA court.)

“We’ll start losing intelligence capabilities,” Senator Christopher S. Bond of Missouri, the ranking Republican on the Intelligence Committee, said in an interview.