"The president wasn't even aware where this information came from. He wasn't briefed on the source or method of the information either," McMaster said at a press briefing.
The Washington Post reported Monday that Trump disclosed classified information in a meeting with Russian officials last week. McMaster initially called the story "false" but today applied that term to the premise of the story.
"What was shared was wholly appropriate, given the purpose of that conversation and the purpose of what the president was trying to achieve through that meeting," McMaster said.
When pressed by ABC News' Jonathan Karl, McMaster would not say if Trump disclosed classified information. Trump said in a pair of tweets Tuesday he had the "absolute right" to share "facts" with the Russians.
"We don't say what's classified, what's not classified. What I will tell you again is that what the president shared was wholly appropriate," McMaster said.
On Monday he said, "At no time were intelligence sources or methods discussed. And the president did not disclose any military operations that were not already publicly known."
"The president was emphasizing we have some common interests here. We have to work together in critical areas," McMaster said.
"So this was the context of the conversation, in which it was wholly appropriate to share what the threat was, as a basis for common action and coordination," he said.
After addressing the press with Turkish President Recep Tayyip Erdogan, who is visiting the White House today, Trump said he "had a very, very successful meeting" with the Russian foreign minister last week.
"As Gen. McMaster said, I thought he said and I know he feels that we had actually a great meeting with the foreign minister, so we're going to have a lot of great success over the next coming years," he told reporters before turning the discussion to his plans for cooperation with Turkey.