WASHINGTON — The executive branch will not eavesdrop on the computer keystrokes and Internet use of members of Congress and legislative staff members with security clearances as part of its stepped-up efforts to prevent unauthorized disclosures of classified information, the nation’s top intelligence official told lawmakers on Friday.

The director of national intelligence, James R. Clapper Jr., made that promise in a letter to Senators Charles E. Grassley, Republican of Iowa, and Ron Wyden, Democrat of Oregon. The lawmakers had raised constitutional concerns about a new “insider threat” detection program amid a controversy over the C.I.A.’s search of computers used by Senate staff members who were at a C.I.A. site preparing a report on agency interrogation practices during the Bush administration.

Last month, Mr. Grassley and Mr. Wyden sent a letter to Mr. Clapper saying that “especially in light of recent events” they wanted to ensure that the Obama administration did not think it could monitor the computer use of legislative officials. They also raised concerns about whether the program could deter executive branch officials from raising whistle-blower complaints with lawmakers.

Responding Friday in a letter obtained by The New York Times, Mr. Clapper said that the monitoring of computer use that he was putting in place would apply only to secure networks in the executive branch and would not extend to congressional computer systems. However, Mr. Clapper said, “when legislative branch personnel access a national security system used or operated by the executive branch, they are of course subject” to user activity monitoring on that system.