President Clinton could face impeachment charges if he ignores a grand jury subpoena to testify about his relationship with a former White House intern, the chairman of the Senate Judiciary committee warned Sunday.

"The fact that he would ignore and violate a subpoena would certainly be grounds to file articles of impeachment," U.S. Sen. Orrin Hatch, R-Utah, said on CBS's "Face the Nation" program.The statement followed reports that Clinton is expected to provide testimony in some form to a grand jury probing whether he committed perjury in denying a sexual affair with Monica Lewinsky.

Although Clinton has resisted requests by independent counsel Kenneth Starr that he voluntarily provide testimony, those close to him say that Starr's use of a subpoena has changed the president's approach.

The White House publicly signaled a new willingness to reach an agreement Friday after the subpoena was issued, according to sources. A compromise could let Clinton give his version of events without having to appear physically before jurors, a source said.

Hatch said that while Starr was within his rights to call Clinton to the court house, the independent prosecutor should be flexible. "The president is a very busy man and we should do everything we can to accommodate him and his schedule in the difficult job that he has," Hatch said.

But he added that Clinton "has an obligation as the highest official in government, sworn to uphold the Constitution and laws of this country" to respond to the subpoena.

"If he doesn't do that I think that public opinion would turn overwhelmingly against him," Hatch said.

Meanwhile, Clinton senior adviser Rahm Emmanuel told NBC's "Meet the Press" that Clinton's lead private attorney has been instructed to work with Starr.

"The President wants to get the information the grand jury needs and has instructed David Kendall to talk to Mr. Starr to do exactly that," Emmanuel said.

During a fund-raising stop Sunday in Aspen, Colo., Clinton ignored questions shouted by reporters concerning the subpoena. And White House spokesman Barry Toiv said the White House would not comment on the issue nor confirm the existence of subpoenas.

But Toiv did say that Kendall had been in discussions with Starr's office about supplying information sought by Starr. "That's a process that's ongoing," Toiv said.

But Sen. Arlen Specter, a Pennsylvania Republican who chairs the Senate Government Affairs Committee, said that ignoring a subpoena would not be grounds for impeachment. "I do not believe that ignoring a subpoena would be grounds for impeachment," Specter said during a CNN interview after hearing Hatch's remarks and, he said, after checking the U.S. Constitution. Hatch said the president could fight the subpoena all the way to the U.S. Supreme Court. But if Clinton lost the battle, there could be a constitutional crisis, he said.