Sen. John McCain issued a sharp rebuke of President Trump after it was reported Saturday that he believed Vladimir Putin's sincerity when Putin asserted that he was not complicit in interfering in the 2016 U.S. election.

“President Trump today stated that he believed Vladimir Putin is being sincere when he denies Russian interference in the 2016 presidential election," McCain, R-Ariz., who is also chairman of the Senate Armed Services Committee, said in a statement.

Trump and Putin spoke briefly a few times at a conference in Vietnam, he told reporters afterwards. He said he, one again, pressed Putin on the issue of Russian meddling, which he said Putin denied. Trump indicated that Putin was sincere in his assertion. "I think that he is very, very strong in the fact that he didn’t do it," Trump said, according to a press pool report.

“There's nothing ‘America First’ about taking the word of a KGB colonel over that of the American intelligence community," McCain said, knocking Trump's foreign policy plan.

Trump's talk of Putin's denials stands in contrast to the conclusion of multiple U.S. intelligence agencies in January that Russia was behind the hacking of emails of the Democratic National Committee and officials involved in Hillary Clinton's campaign. There are now a number of investigations, one federal probe headed by special counsel Robert Mueller and a handful of others in Congress, looking into Russian interference and whether the Trump campaign colluded with the Kremlin.

The Central Intelligence Agency broke with Trump and stood by its prior conclusion, via a statement issued Saturday.

The second part of McCain's statement appears to gripe about Trump's claims that he aims to cooperate with Russia to end the six-year-plus bloody conflict in Syria.

"There's no ‘principled realism’ in cooperating with Russia to prop up the murderous Assad regime, which remains the greatest obstacle to a political solution that would bring an end to the bloodshed in Syria," McCain said. "Vladimir Putin does not have America's interests at heart. To believe otherwise is not only naive but also places our national security at risk.”

A nearly identical joint statement issued separately by the Kremlin and the U.S. State Department on Saturday said the two leaders agreed "there is no military solution to the conflict in Syria."

Russia supports the Syrian President Bashar Assad's regime while the U.S. has backed some rebel groups – some of whom oppose Assad – that are fighting ISIS. In July, the U.S. and Russia reach 'de-escalation zone' agreement in Syria.

Over an hour after McCain issued a statement, Trump, from Vietnam, tweeted that a good relationship with Russia and its leader, Putin, could be beneficial to the U.S. and the international community.

"When will all the haters and fools out there realize that having a good relationship with Russia is a good thing, not a bad thing," he tweeted. "There always playing politics - bad for our country. I want to solve North Korea, Syria, Ukraine, terrorism, and Russia can greatly help."