Senators of both parties sharply questioned Tulsi Gabbard, President Trump’s pick to be director of national intelligence, during a tense and at times combative hearing on Thursday that could signal a challenging confirmation fight.

Over more than two hours, members of the Senate Intelligence Committee, sounding by turns skeptical and outraged, pressed Ms. Gabbard about her 2017 meeting with Bashar al-Assad, the Syrian dictator who was ousted in December, and her statements blaming the United States and NATO for provoking the Russian invasion of Ukraine in 2022.

But it was her refusal to fully denounce Edward J. Snowden, the former National Security Agency contractor who leaked reams of classified information about government surveillance programs in 2013, that seemed to elicit the most concern among both Republicans and Democrats.

She refused, under repeated questioning by members of both parties, to declare that Mr. Snowden was a “traitor,” replying instead that he “broke the law” and that she would seek to prevent similar leaks in the future, if she were confirmed to oversee the nation’s 18 spy agencies.

Ms. Gabbard said that Mr. Snowden, whose most significant disclosure was the bulk data collection of Americans’ phone metadata, had “exposed egregious, illegal and unconstitutional programs that are happening within our government.”

Her responses seemed to leave several committee members unsatisfied.

“Is Edward Snowden a traitor to the United States of America?” Senator Michael Bennet, Democrat of Colorado, asked in a thunderous voice. “That is not a hard question to answer when the stakes are this high.”

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