Poisoned: Russian ex-spy Sergei Skripal, 66, and his daughter Yulia Skripal, 33.
The sanctions, according to the State Department statement, will take place on August 22, 2018, following a "15-day congressional notification period".
A State Department official Wednesday said the delay in issuing the sanctions did not reflect any hesitation on the part of the Trump administration.
In March, the Trump administration ordered 60 Russian diplomats - all of whom it said were spies - to leave the United States and closed down Russia's consulate in Seattle in response to the Skripal case.
"The administration is rightly acting to uphold worldwide bans on the use of chemical weapons", said Ed Royce, R-Calif., chairman of the House Foreign Affairs Committee. The Skripals survived being targeted with a Russian-created novichok nerve agent.More news: Woman helps man short on cash -- it was Keith Urban
There would be exemptions for space flight activities as well as areas covering commercial passenger aviation safety, the official added.
They believe the bottle was then dropped somewhere in the city, where Charlie Rowley picked it up and gave it to his partner Dawn Sturgess, who died after apparently spritzing it on her wrist.
London and its allies have accused Moscow of trying to kill the Skripals and says the two cases are likely linked. The statement anticipated the sanctions would go into effect around August 22 in line with the Chemical and Biological Weapons Control and Warfare Elimination Act of 1991.
The State Department announced a number of possible exceptions to the sanctions announced Wednesday.
The news came as Republican US Senator Rand Paul said he had delivered a letter from US President Donald Trump to Russian President Vladimir Putin proposing cooperation. "The UK welcomes this further action by our United States allies", a spokesman for the UK Foreign Office said in a statement. The US still wants to maintain relations with Moscow, despite the new sanctions.
The White House has not said whether the poisonings came up during his meeting with Putin.