The White House on Thursday withdrew the nomination of Dr. Dave Weldon, a Republican and former congressman, to lead the Centers for Disease Control and Prevention just hours before he was to have appeared at a Senate confirmation hearing.

Reached by phone, Dr. Weldon said he had learned of the decision on Wednesday night and had been told by a White House official that “they didn’t have the votes to confirm” his nomination.

In a statement released later on Thursday, Dr. Weldon, 71, blamed Senator Susan Collins, Republican of Maine and a member of the Senate health committee, and Senator Bill Cassidy, Republican of Louisiana and the committee’s chairman, for torpedoing his nomination.

A spokesman for Mr. Cassidy said the senator had been “looking forward” to the confirmation hearing. Ms. Collins’s office disputed Dr. Weldon’s account.

“I did not express concerns to the White House. I had some reservations, but I certainly had not reached a final judgment,” Ms. Collins said Thursday.

The withdrawal of Dr. Weldon’s nomination, which followed concerns raised during a meeting on Tuesday with Republican Senate aides, is a significant setback for Robert F. Kennedy Jr., the new secretary of health and human services.

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