The disclosure contradicts popular perceptions that the government is sweeping up virtually all domestic phone data. It is also likely to raise questions about the efficacy of a program that is premised on its breadth and depth, on collecting as close to a complete universe of data as possible in order to make sure that clues aren’t missed in counterterrorism investigations.

In 2006, the officials said, the NSA was collecting nearly all records about Americans’ phone calls from a number of U.S. companies under a then-classified program, but as of last summer that share had plummeted to less than 30 percent.

The government is taking steps to restore the collection — which does not include the content of conversations — closer to previous levels. The NSA is preparing to seek court orders to compel wireless companies that currently do not hand over records to the government to do so, said the current and former officials, who spoke on condition of anonymity to discuss internal deliberations.