U.S. Director of National Intelligence Dan Coats said on Tuesday he had not seen evidence of Russia trying to meddle in the 2018 U.S. midterm elections, but it is "highly likely" Moscow will try to do so.

"We have not seen evidence of a robust effort yet on the part of Russia, but we know their malign activities continue to exist," Coats told a Senate armed services committee hearing.

"It's highly likely that they will be doing something. We just don't know how much and when and where," he said.

Coats said he expected the U.S. Treasury to announce sanctions on Russia over election meddling as soon as next week.

His comments came not long after Treasury Secretary Steven Mnuchin made a similar announcement at a House subcommittee hearing, albeit with a slightly different timeline.

"I expect in the next several weeks we will be moving forward with sanctions on Russia as a result of the act," said Mnuchin.

Treasury Secretary Steven Mnuchin says the president is 'fully supportive' of the decision to implement sanctions. (Susan Walsh/Associated Press)

He said Trump is "fully supportive" of the actions.

It wasn't immediately clear what form the sanctions would take.

U.S. preparedness questioned

Democrats have criticized Trump for a perceived failure to raise appropriate alarm about the attempts by a rival to interfere with domestic politics. After the office of U.S. special counsel Robert Mueller charged 13 Russians and three firms last month with interfering in the 2016 presidential vote, Trump focused almost solely in statements on social media on how he believed the indictments personally vindicated him of any charges of having colluded with Russia.

When his national security adviser H.R. McMaster said a day after the Mueller indictments were announced that the Russia meddling was "beyond dispute," Trump admonished him on Twitter.

Russia has denied meddling in the most recent presidential election.

In November, Trump said he believed the conclusion of U.S. intelligence agencies that there had been meddling. But Trump also said he believed Vladimir Putin was sincere when he said Russia didn't interfere.

In recent weeks, officials and politicians have argued for bolstering U.S. defences against cyber intrusions in order to avoid a repeat scenario as all House seats and a third of Senate seats will be contested in November.

Admiral Mike Rogers, director of both the U.S. Cyber Command and the National Security Agency, testified that the U.S. response to Russian meddling and disinformation campaigns has not been strong enough to deter Moscow's activities.

As well, a recent report by Senate Democrats took Trump to task for offering no strategic plan to safeguard the U.S.

They urged, among other recommendations, that the administration fully fund and utilize the State Department's Global Engagement Center, which has a mandate to counter propaganda and disinformation from international terrorist organizations and foreign countries.

A report by the New York Times this week claimed that $120 million US that had been allocated for the centre in late 2016 has not been touched or used under the leadership of Trump and Secretary of State Rex Tillerson.

None of the analysts in the unit speak Russian, the Times reported.

Putin told NBC News in an interview broadcast this past weekend that Russia would not be extraditing any individuals to the U.S. as a result of the Mueller probe. He said any allegations, even if true, were not the work of the Russian government.

Putin said on Tuesday in Moscow that the Russian nationals who have been accused could be prosecuted in Russia if they were found to have broken Russian law, the TASS news agency reported.