Rep. Carolyn B. Maloney plans to announce a primary challenge to Sen. Kirsten Gillibrand, D-N.Y., on her Web site Thursday morning, according to two sources including a member of the delegation.

Maloney disputed that characterization in a brief hallway interview.

“Where did you get that from?” she asked. “It’s not true.”

Regardless of the timing or venue, several members of the New York delegation, including Reps. Jerrold Nadler and Anthony D. Weiner, said Maloney has told them she will run. She has also told political allies in her “silk stocking” district on Manhattan’s Upper East Side that she is preparing a bid.