Washington ? President Barack Obama said Wednesday night that waterboarding authorized by former President George W. Bush was torture and that the information it gained from terror suspects could have been obtained by other means. “In some cases, it may be harder,” he conceded at a White House news conference capping a whirlwind first 100 days in office.

Obama also expressed much greater optimism now than a month ago that Chrysler could remain a “going concern,” possibly without filing for bankruptcy or with a “very quick” one. Obama did not say so, but Italian automaker Fiat Group SpA is expected to sign a partnership agreement with Chrysler LLC by today as part of negotiations to keep the struggling U.S. automaker alive without bankruptcy protection.

The president gave assurance that one way or another Pakistan’s nuclear arsenal would not fall into the hands of Islamic extremists. He said he was confident “primarily, initially” because he believes Pakistan will handle the issue on its own. But he left the door open to eventual U.S. action to secure the weapons if need be.

The prime-time news conference was the third of Obama’s presidency and the first not dominated by a recession that has thrown millions of Americans out of work.

At a town-hall style meeting in Missouri earlier in the day, as well as in the White House East Room, Obama said progress has been made in rebuilding the economy, yet more remains to be done.

“You can expect an unrelenting, unyielding effort from this administration to strengthen our prosperity and our security — in the second hundred days, and the third hundred days, and all the days after,” he said in opening his news conference.

He called on Congress to enact his ambitious all-at-once agenda, including education spending to produce a better-trained work force, greater support for renewable energy development, a high-priced system for companies to buy and sell rights to emit dangerous pollutants, a vast expansion of health insurance and new rules to rein in the riskiest Wall Street behavior.

Though Obama’s most notable legislative triumphs to date have been enacted on party-line votes, he said he remains eager for bipartisan cooperation with Republicans. But, he said, “I can’t sort of define bipartisanship as simply being willing to accept certain theories of theirs that we tried for eight years and didn’t work and the American people voted to change.”

Obama said Pennsylvania Sen. Arlen Specter’s switch from Republican to Democrat wouldn’t automatically change the math on legislation because of Specter’s independence, nor give him a “rubber-stamp Senate.” Specter gave majority Democrats 59 votes in the Senate, pushing them one step closer to the 60 needed to overcome Republican filibusters.

But the party change would “liberate” Specter to cooperate with Democrats more than he has in the past, Obama said.

The president also said he was “absolutely convinced” he had acted correctly in banning tough interrogation techniques including waterboarding, which simulates drowning, and in making public the Bush administration memos detailing their use on terrorist suspects. “Not because there might not have been information that was yielded by these various detainees … but because we could have gotten this information in other ways, in ways that were consistent with our values, in ways that were consistent with who we are.”

Obama has come under heavy criticism for his actions from former Vice President Dick Cheney and other Republicans. They have urged Obama to release memos they say will show the tough methods were successful in obtaining information.

Obama told reporters he has read the documents Cheney and others are referring to but said they are classified and declined to discuss their details. In a White House exchange with House Republican leader John Boehner last week, Obama said the record was equivocal.

The news conference lasted an hour and covered topics ranging from the outbreak of swine flu — which Obama referred to as the H1N1 virus, evidently in deference to U.S. pork producers — to abortion and the recent flare-up in violence in Iraq.