Ridge said he will continue to meet informally with lawmakers, but he has no intention of testifying because he is an adviser to the president, not a Cabinet member obliged to appear on Capitol Hill.
"I don't think you can compromise the principle of separation of powers," Ridge said on ABC's "This Week."
"I do think that we should continue our discussions to determine whether or not there's a forum that both the Congress and the White House can agree is appropriate."
Some Democrats have raised the possibility of subpoenaing Ridge to compel his testimony.
The Bush administration wants spending on domestic security to double next year, to $38 billion. Ridge argues that he has no authority over any federal agency and does not control any appropriations, but only makes recommendations.
Some lawmakers contend that Ridge is more powerful than most advisers because he coordinates spending by more than 80 federal agencies.
House Speaker Dennis Hastert defended Ridge's refusal to appear before the Senate Appropriations Committee, which Democrats control.
"I'm not sure that the adviser to the president ought to be grilled by Congress, because I think he owes the president his best information, his best knowledge," Hastert, R-Ill., said on "Fox News Sunday."
On other matters, Ridge warned that Americans still should be wary of another terrorist attack. Pressed to offer an example of a credible threat, Ridge pointed to al-Qaida and the possibility that members may have entered the United States.
"Over the past couple of years we've had 300 million noncitizens enter and exit, and we have to assume ... there may be several in the United States today that want to do us harm," he said. "We have to be prepared."