At a news conference wrapping up the two-day North Atlantic Treaty Organisation summit in Brussels, Trudeau was pressed to provide more details about the US president's sudden insistence that allies have agreed to spend more - and to do it more quickly.
He said allegations that Russian intelligence hacked Hillary Clinton's campaign team was a "witch hunt" and an obstacle in his relationship with Mr Putin.
Mr Trump will leave Britain this weekend for a meeting with Mr Putin in Helsinki, Finland, on Monday.
In Friday's indictment, the Justice Department accuses the Russian officers of hacking into Democratic accounts during the 2016 election campaign and releasing the stolen information in the months before Americans headed to the polls.
While not expressing outright support for the meeting with Russian Federation, which is to take place on Monday, McCain said Thursday that that summit represented an opportunity for Trump "to demonstrate his willingness to defend America" against its adversaries.
But the president indicated he did not expect much progress on the issue. "But I will absolutely, firmly ask the question", he added.More news: Trump questions how Russian Federation probe can 'proceed' given Federal Bureau of Investigation agent's private comments
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After German Chancellor Angela Merkel hit back at US President Donald Trump for taunting Germany as "Russia's captive" for its alleged overdependence on Moscow for energy saying Berlin took its independent decisions, the Kremlin also lashed out at the American president over the same, saying Trump said so to bully Europe into buying its own energy, Reuters reported. "I think that we would have a chance to have a very good relationship with Russian Federation and a very good relationship with President Putin".
Breaking from a carefully scripted session that was to focus on Ukraine and Georgia, one source said Trump "forcibly restated his position on wanting North Atlantic Treaty Organisation members to reach 2 percent spending target to a short a deadline".
"This is something that we believe in deeply", Trudeau said of the new Iraq mission.
But less than three hours later, the California Democrat joined the chorus of party members calling for the meeting to be canceled.
"The aim of this meeting is to begin setting right the negative state of bilateral relations, to agree on concrete measures to improve them and to establish a more or less acceptable level of trust", Ushakov said. "The Russian state has never interfered and has no intention of interfering in the USA elections", Putin's foreign affairs adviser, Yuri Ushakov, said Friday.
Moreover, Trump's remarks on North Atlantic Treaty Organisation seem to suggest that Europe must pay the United States for protection from Russian Federation, when this is not how the alliance is meant to function. The city has a long history of acting as a diplomatic bridge between the USA and Russian Federation.