The battle over a Reagan administration secrecy pledge escalated yesterday when Sen. Charles E. Grassley (R-Iowa), citing what he called the "stubbornness and unreasonableness of administration officials," called on hundreds of thousands of federal employes to refuse to sign it.

The rare senatorial call for, in effect, civil disobedience drew a swift rebuke from the administration official in charge of enforcing the secrecy pledge as well as the president of a federal employe union seeking to overturn it.

By signing the one-page document, Standard Form 189, federal employes pledge not to disclose any information that is classified or "classifiable." Administration officials have argued that the form is needed to stanch a flood of unauthorized leaks of secret information, currently running to about 100 to 110 reported cases annually, according to testimony presented to a House Post Office and Civil Service subcommittee yesterday.

But Grassley, calling the pledge a "broad grab for power" by administration officials, told the House panel that the form's true purpose was not to protect secrecy but rather "to place a blanket of silence over all information generated by the government . . . . I would urge all federal employes to refrain from signing SF 189."

"That's tantamount to telling all federal workers they ought to go on strike," Joseph M. Peirce, president of the National Federation of Federal Employes, said later about Grassley's comment. "I think it was ill-advised."

About 1.7 million civilian and military personnel have signed the form since it was initially distributed in the fall of 1983. And, 660,000 government workers who potentially have access to secret information have not yet been asked to sign. Twenty-four -- including noted Pentagon whistle-blower A. Ernest Fitzgerald and Air Force training manager Louis C. Brase -- have refused to do so and their security clearances have been threatened.

The fight over the secrecy form last flared when two federal workers' unions filed suits charging that the pledge violates the employes' constitutional rights. In an attempt to defuse the issue, Grassley began meeting with administration officials to negotiate a compromise on the form's wording.

Critics charged that the form's reference to "classifiable" information is so broad as to potentially encompass anything that crosses a federal workers' desk. They noted the phrasing does not appear on a parallel form that employes of government contractors are required to sign.

Grassley's efforts broke down last week when administration officials refused to agree to a more restrictive definition of "classifiable" demanded by the senator. As it now stands, "classifiable" information is defined as unmarked intelligence or data that an employe knows is in the process of being classified as well as information that "he reasonably should know" is in the process of being reviewed for classification.

In that case, "the unauthorized disclosure is negligent," said Steven Garfinkel, director of the General Service Administration's Information Security Oversight Office, which is charged with enforcing the secrecy pledge.

Rep. Gerry Sikorski (D-Minn.), the chairman of the subcommittee, said later he endorsed Grassley's call on federal workers to refrain from signing the form, adding that it was "the most significant" testimony.

It was unclear, however, what impact such a call would have, given that most of the affected federal workers have signed the pledge. Moreover, administration officials recently agreed that, while the unions' suits are pending, they will no longer revoke employes' security clearances solely for refusing to sign the form.

But Garfinkel confirmed yesterday that administration "policy" is to continue to ask federal workers to sign the form, and Grassley's comments could well make that task more difficult. "It will obviously encourage people not to sign," Garfinkel said.

Garfinkel said he still believed Grassley and the administration were close to reaching an agreement. But, he added, despite the temporary lapse in punitive sanctions, the administration was by no means ready to abandon its insistence on having the forms signed in the future. "Nobody has a right to classified information," he said.