WASHINGTON (AFP) - The White House is weighing additional sanctions against Russia, senior administration officials said on Wednesday (Feb 21) , pushing back against allegations that Donald Trump has been a soft touch on Moscow.

Speaking on condition of anonymity, officials said a "task force" has been set up to address potential meddling in the 2018 congressional elections and work is underway to introduce sanctions in response to Moscow's 2016 campaign.

Underscoring one step, one senior administration official said that Washington has already warned governments around the world that they could face sanctions if they carry out "significant transactions" with the Russian military.

That includes NATO ally Turkey, which has publicly announced the purchase of a Russian S-400 air defence missile system.

A second official said that "a couple of big countries" were reconsidering their purchases as a result.

Those type of sanctions were part of a package of measures passed by Congress approved last July, that were opposed by the White House.

Trump's vocal opposition to the package - which entered into law earlier this year - has raised questions about whether the administration is dragging its feet.

Officials admitted no specific sanctions had been introduced yet, but said that was because the administration was doing its due diligence, rather than an attempt to slow-walk the process.

The first official also stressed the need to avoid leaks that could tip off potential sanction targets, allowing them to move money out of bank accounts or take other mitigating steps.

"We are doing an awful lot of work, we are taking this very seriously, it is a national security issue," the official said, answering criticism.

"I would hope you would just give us a little bit of an indulgence to do some of these things behind the scenes and be able to reveal them when we can." "We would like to get after these guys and we would like to catch them in the act and not enable them to change course ... so that we have a harder time detecting them."

One example given was the shuttering of the Russian consulate in San Francisco, which was ordered closed late last year, taking Moscow by surprise.

"The Russians did not see that coming" said the first official, adding, "which is an absolute bloody miracle frankly" given reporting before a decision was made.