John Brennan
© AFP 2017/ Jewel Samad
A collusion between Russian officials and members of US President Donald Trump campaign cannot be confirmed, former CIA Director John Brennan stated during a testimony at the US Senate on Tuesday.

Both Trump and numerous Russian officials, including President Vladimir Putin, have repeatedly denied claims of alleged Moscow's collusion with the US president's campaign, as well as of the Kremlin's interference in the 2016 US election.

"I encountered and am aware of information and intelligence that revealed contacts and interactions between Russian officials and US persons involved in the Trump campaign," Brennan stated. "I don't know and cannot confirm if collusion existed."

Brennan said that he had no knowledge of President Donald Trump's alleged attempts to ask US intelligence officials to stop the investigation about allegations his campaign colluded with Russia during the 2016 US election.

When asked whether Trump has made any efforts to enlist the support of intelligence officials to push back on Russia collusion issue, Brennan stated, "I am unaware of it."

Brennan also said that he did not know whether Trump had tried to pressure former FBI Director James Comey to drop an investigation into ex-National Security Adviser Michael Flynn.