Sen. Dianne Feinstein, whose vote on Supreme Court nominee John Roberts could guide other Democrats, said she will scrutinize his views on abortion and congressional authority to set social policy.

Feinstein said Monday that the impending debate over Roberts' nomination was a "big, big deal."

"I don't think in the last couple of decades there has been a Supreme Court appointment that could more tip the balance of the court," Feinstein said in a speech to several hundred Silicon Valley business executives. "That's how mega this vote is."

President Bush nominated Roberts, a federal appeals court judge, in July to replace retiring Justice Sandra Day O'Connor. Senate Judiciary Committee hearings are set to begin shortly after Labor Day.

Feinstein, a moderate Democrat, has emerged as a pivotal figure. Republicans have enough votes to send Roberts' nomination to the full Senate for consideration, but Feinstein's committee vote could guide other Democrats.

As the only woman on the 18-member committee, Feinstein said she has a "special role and a special obligation" in grilling Roberts. That is particularly true in probing his views about the 1973 Roe vs. Wade decision legalizing abortion, she said.

"I happen to feel that it would be very difficult for me to vote yes on a nominee I thought would overturn Roe vs. Wade," she said. "What I need to find out is what his views are."

Feinstein met privately with Roberts shortly after he was nominated. Since then, Roberts' writings on many matters that come before the court - including sex discrimination, race relations and environmental protection - have emerged in thousands of pages of documents released by the Reagan Library and the National Archives.

Roberts served in the Justice Department and the White House counsel's office during the Reagan administration.

Feinstein said she had not yet been briefed on the content of those documents.

In her remarks Monday, Feinstein also said the Supreme Court under Chief Justice William Rehnquist had restricted congressional authority to pass legislation.

Feinstein said the Rehnquist court had used the Constitution's interstate commerce clause and the equal protection clause of the 14th Amendment to weaken or invalidate at least three dozen federal laws in the last decade. She said those included the Violence Against Women Act and the Brady handgun law.

She described those two constitutional provisions as the "the primary sources of congressional power" to enact social policy.

Whether Roberts favored such an approach would heavily influence her decision on whether to vote for him, Feinstein said.

"I would like to come away with the view that he was not going to be one who would further restrict and bind lawmakers' hands and keep them from enacting legislation that the people of this country want," Feinstein said.

Feinstein is scheduled to deliver further remarks on the Supreme Court and the Roberts nomination Wednesday during a speech before the Los Angeles County Bar Association.