WASHINGTON — In a tense confrontation with President Obama’s closest adviser on Thursday, a group of Senate Democrats accused the White House of trying to censor significant details in a voluminous report on the use of torture by the Central Intelligence Agency.

During a closed-door meeting on Capitol Hill with Denis R. McDonough, the White House chief of staff, the senators said that the White House was siding with the C.I.A. and trying to thwart negotiations over the report’s release. The negotiations have dragged on for months because of a dispute over the C.I.A.'s demand that pseudonyms of agency officers be deleted from the report.

The C.I.A., supported by the White House, has argued that even without using the real names of the officers, their identities could still be revealed.

According to several people in attendance, the meeting was civil, but neither side gave ground, and it ended without resolution. The Senate Intelligence Committee spent five years working on the 6,000-page report, which is said to provide grim details about the torture of detainees in C.I.A. prisons during the Bush administration, and describe a persistent effort by C.I.A. officials to mislead the White House and Congress about the efficacy of its interrogation techniques. The committee voted this year to declassify the report’s executive summary, numbering several hundred pages, but the fight over redactions has delayed the release.