I believe Trump did explicitly say that firing Comey was not an attempt to end the investigation. According to NBC’s summary:
Asked by Holt if by firing Comey he was trying to send a "lay off" message to his successor, Trump said, "I'm not."
”If Russia did anything, I want to know that," he said.
Of course, the issue of what Trump said in this interview is separate from the issue of whether he was telling the truth. I’m not sure I believe Trump’s claims, but I’m inclined to agree with NN’s about what he actually said?