"Armitage did not slip me this information as idle chitchat, as he now suggests. He made clear he considered it especially suited for my column," Novak wrote.
Armitage gave a different version of events to CBS News. The former Bush administration deputy secretary of state said he disclosed Plame's CIA status in response to an "offhand question" from Novak.
"I didn't put any big import on it and I just answered and it was the last question we had," Armitage said.
Plame and her husband, Joseph Wilson, filed a lawsuit in July against Vice President Cheney, Lewis "Scooter" Libby and Karl Rove, claiming that they had violated her constitutional rights and discredited her by disclosing that she was an undercover CIA operative.
Armitage was added to the lawsuit on Wednesday, following news that Armitage was Novak's initial source for a column he wrote identifying Plame as a CIA officer.
Armitage told CBS News correspondent David Martin last week that he was sorry for what he characterized as an inadvertent disclosure.
"I feel terrible every day," Armitage said, "I think I let down the President. I let down the Secretary of State. I let down my department, my family, and I also let down Mr. and Mrs. Wilson."
Special Prosecutor Patrick Fitzgerald has investigated the leak of Plame's name for years and has not charged anyone with intentionally leaking her identity. Libby is under indictment; he's charged with lying to authorities about his conversations with reporters.