(AP) - President Barack Obama expressed optimism Wednesday night that Chrysler could remain a "going concern," possibly without filing for bankruptcy, a generally upbeatassessment on one of numerous challenges he has confronted in a whirlwind first 100 days in office.

Obama said "unions and creditors have come up with a set of potential concessions that they can live with," adding, "All that promises the possibility that you can get a Chrysler-Fiat merger."

Obama made his remarks at a prime-time news conference that capped his 100th day in office, a time of national testing given a deep economic recession and unprecedented credit crunch.

At his news conference, Obama also said he had no second thoughts about having approved the release of Bush administration memos detailing the use of waterboarding and other harsh interrogation techniques used on terrorist suspects.

"I do believe that it is torture," he said flatly of waterboarding, which simulates drowning. He appeared to acknowledge that useful information had been obtained in interrogations in which it was used, as assessment made in a memo by his administration's top intelligence official.

Asked about Chrysler, he was notably more upbeat that an administration report issued nearly a month ago.

"I'm feeling more optimistic," he said.

Obama did not say so, but Italian automaker Fiat Group SpA is expected to sign a partnership agreement with Chrysler LLC by Thursday as part of negotiations to keep the struggling U.S. automaker alive without bankrupcty protection.

On a political matter, Obama said he thought that Pennsylvania Sen. Arlen Specter's switch Tuesday from Republican to Democrat would "liberate him to cooperate on critical issues like health care, like infrastructure and job creation, areas where his inclinations were to work with us but he was feeling pressure not to."

Obama's intensive schedule for the day demonstrated the degree to which the administration saw both possibility and peril in the 100-day marker - a symbolic milestone since Franklin Roosevelt took office in the depths of the Great Depression in 1933.

Presidential aides have derided it as a media-created "hallmark holiday" in which the White House participates reluctantly. But they also recognize it is a time frame by which all modern presidents are judged, at least initially, and which can produce negative narratives that dog administrations for years. So the White House has jumped into the celebration with both feet, making high-level Obama advisers available anywhere they were needed over the last week and crafting the president's day to maximum advantage.