Moscow(CNN) The Kremlin has described the Trump administration's decision to impose further sanctions against Russia following the poisoning of former Russian spy Sergei Skripal and his daughter in the UK earlier this year as "categorically unacceptable" and "illegal," and has vowed to "work on retaliatory measures."
The US State Department announced Wednesday that sanctions would be imposed under a chemical and biological warfare law and would go into effect around August 22. The statement also accused Russia of violating international law.
During a regular press call on Thursday, Russian President Vladimir Putin's spokesman Dmitry Peskov said that Russia "does not have anything to do with the use of chemical weapons" and that the sanctions were "unacceptable" and "illegal."
Later on Thursday, Foreign Ministry spokeswoman Maria Zakharova said that Russia "will work on retaliatory measures" in response to the sanctions.
Skripal and his daughter Yulia Skripal were hospitalized and treated for a nerve-agent attack in March. Yulia Skripal was discharged from the hospital in April, and her father was released in May. The UK and its allies have blamed Russia for the attack, an accusation the Kremlin has repeatedly rebuffed.
"Once again we totally reject any allegations of possible Russian government involvement over what happened in Salisbury," Peskov said Thursday, adding that "Russia did not have and does not have anything to do with the use of chemical weapons."
The first set of sanctions targets certain items the US exports to Russia that could have military uses -- so-called dual-use technologies. These are sensitive goods that normally would go through a case-by-case review before they are exported. With these sanctions, the exports will be presumptively denied.
A senior State Department official said Wednesday that there could be exceptions.
The US would then require Russia to assure over the next 90 days that it is no longer using chemical or biological weapons and will not do so in the future. Additionally, the criteria in the law call for Russia to allow on-site inspectors to ensure compliance.
The official said that if Russia did not meet the demands, the US "will have to consider whether to impose a second tranche of sanctions as specified by the statute."
A former Defense Department official, Mark Simakovsky, said Wednesday that a second tranche would target Russian exports to the US and theoretically could include restrictions on flights by the state airline Aeroflot as well as a downgrade of diplomatic relations.
When asked Thursday about the possibility of a ban on Aeroflot, Peskov labelled the US administration an "unpredictable participant in international affairs," adding "you can now expect anything."
"President Putin said in Helsinki that Russia still has hopes for the creation of a constructive relationship with Washington," Peskov said.
"This relationship is not only in the interests of our peoples but also for strategic stability and security in the world. Putin has said more than once and he has demonstrated a constructive approach and his readiness to find a way out of difficult situations and discuss difficult questions. No one should doubt that Putin will not keep to this approach."
"We are sorry that often we are not met with cooperation on this account."
The United Kingdom welcomed the move from the US on Wednesday. In a short statement, a government spokesperson said, "The strong international response to the use of a chemical weapon on the streets of Salisbury sends an unequivocal message to Russia that its provocative, reckless behavior will not go unchallenged."