A former NATO commander described as "souring" the relations between US President Donald Trump's administration and Russia amid a series of foreign policy collisions between the two countries, the media reported.

"That relationship between the Trump administration and Russia is gradually going downhill, because I think the senior members of the Trump administration are beginning to realise that Russia is not a force for good in the world," retired Admiral James Stavridis told a radio station here on Sunday.

"I think reality is setting in about how difficult a partner (Russian President) Vladimir Putin will be, and I think events in Syria have underlined that for the administration," he added.

Stavridis's comments came days after the US launched a missile strike on a Syrian military air base on April 6, The Hill magazine reported.

The attack was in response to a chemical weapons strike in northern Syria on April 4 allegedly carried out by the regime of President Bashar Assad. The attack killed over 80 civilians including children.

While the US retaliation was largely hailed by world leaders, it drew a bitter response from Russia, a staunch backer of the Assad regime. A spokesman for Russian President Vladimir Putin called the strike an "aggression" and said the U.S. had violated international law.

The attack led the Kremlin to suspend an agreement between the two countries meant to lower the risk of in-flight collisions of US and Russian aircraft in the region.

On the campaign trail, Trump spoke fondly of Putin and expressed a willingness to increase cooperation between the US and Russia, the magazine added.

The Federal Bureau of Investigation and congressional investigators are currently conducting separate probes into Russian meddling in the US presidential election and possible ties between the Trump campaign and Russia.