(CNN) - President Donald Trump said he would not have allowed the CIA to recruit the half-brother of North Korean leader Kim Jong Un "under my auspice."
Trump wouldn't confirm or deny reports that Kim Jong Nam had been working with the CIA prior to being killed in Malaysia in February 2017, saying that he didn't know anything about it.
"I know this: that the relationship is such that that wouldn't happen under my auspices, but I don't know about that. Nobody knows," he said.
The one-time heir apparent had become the black sheep of the Kim family before he was killed, after two women smeared nerve agent on his face in Kuala Lumpur International Airport in February 2017. Lawyers for both women, one Indonesian and the other Vietnamese, argued that their clients hadn't known what they were doing, believing they were taking part in a prank reality TV show.
In an article Monday, the Wall Street Journal claimed that the elder Kim brother had been a source for the CIA and had met with agency operatives several times.
The CIA operative claims are also described in a book about Kim Jong Un by Washington Post reporter Anna Fifield published on Tuesday. "The Great Successor" details meetings between Kim Jong Nam and his handlers in the two countries. The CIA has declined to comment to CNN. Trump took office just a few weeks before Kim Jong Nam's death and repeatedly said on Tuesday he didn't know whether the reports are true.
It comes as negotiations between US and the North Korean governments have stalled after a breakdown in talks at the Hanoi summit between Trump and Kim Jong Un.
Trump said Tuesday that Kim had so far "kept his word" on nuclear and missile testing, even though no new talks between the US and North Korea are currently planned.
"I just received a beautiful letter from Kim Jong Un and I think the relationship is very well, but I appreciated the letter," Trump said Tuesday.
But just hours earlier, at an event in Washington, national security adviser John Bolton told the Wall Street Journal that Kim wasn't complying with the terms agreed at the Singapore summit.
"What they've said was that they're not going to test ballistic missiles, intercontinental range ballistic missiles, or have nuclear tests. That's continued," Bolton said.
"They're doing a lot of other things that still indicate that they have not made a strategic decision to give up the pursuit of deliverable weapons, which is why we continue the maximum pressure campaign."
CNN's Joshua Berlinger contributed to this article.