WASHINGTON -- The battle over Homeland Security Director Tom Ridge's refusal to testify before Congress escalated Tuesday as House Democrats protested Republican plans to have Ridge instead brief members of the House Government Reform Committee informally and in secret.

The closed-door hearing is scheduled for Thursday morning. Attendance is limited to committee members and staff.

The Democrats, led by Reps. Henry Waxman (D-Calif.) and Jan Schakowsky (D-Ill.), demanded in a letter to the committee chairman, Rep. Dan Burton (R-Ind.), that the session be open to the public because Ridge is "the federal official with primary responsibility for protecting the nation against future terrorist attacks."

Kevin Binger, the committee staff director, said Burton would make an official response Wednesday, but it was unlikely he would change his mind.

"We feel this will more efficiently use the time of Gov. Ridge and make for a little freer exchange between the members and Gov. Ridge," Binger said.

The conflict began last month when Ridge refused a request from Senate Appropriations Committee Chairman Sen. Robert Byrd (D-W.Va.) to testify on how the administration intends to spend the $38 billion it budgeted for homeland defense measures in the next fiscal year, twice what was allocated for the current year.

Ridge and the White House argued it would breach the constitutionally protected separation of powers if a presidential adviser were compelled to give sworn testimony involving advice he or she might privately give the president.

Ridge said that Cabinet secretaries and department heads might properly be made to testify but that conversations between a president and his advisers should be privileged.

As an alternative, Ridge said he would make himself available for informal briefings. Last week, he announced he had made arrangements with House Republicans for two such sessions in which sworn testimony would not be required.

But on Friday, Byrd said he would insist on sworn testimony from Ridge, and several Democrats suggested a subpoena might be necessary to compel his appearance.

In their Tuesday letter, the House Democrats insisted that a formal session was necessary to assure fairness and make Ridge be forthcoming.

Noting that Ridge had raised no objection to giving a public briefing, they argued there is no constitutional basis for granting presidential advisers immunity from testifying.

They pointed out that advisers to Presidents Dwight Eisenhower, Richard Nixon and Jimmy Carter gave sworn congressional testimony and that Burton's committee had compelled 20 of President Bill Clinton's advisers to testify.