WASHINGTON/LONDON: The US today said it will impose tough new sanctions on Russia after determining that Moscow used a deadly military-grade nerve agent to kill a former Russian double agent and his daughter in the UK.Sergei Skripal, a former Russian spy, and his daughter Yulia Skripal were hospitalised and treated for a nerve agent attack in March. While Yulia was discharged from a British hospital in April, her father recovered and left the hospital in May.The State Department said in a statement that the sanctions were in response to the use of a 'Novichok' nerve agent in an attempt to assassinate UK citizen and his daughter on March 4.Russia has rejected allegations levelled by the UK that it was behind the deadly nerve-agent attack in the English city of Salisbury.The US, on August 6, determined that the Russian government "has used chemical or biological weapons in violation of international law or has used lethal chemical or biological weapons against its own nationals," State Department spokeswoman Heather Nauert said.The statement said that following a 15-day Congressional notification period, these sanctions will take effect around August 22.The State Department notified Congress yesterday of the first of two potential tranches of sanctions required under the 1991 law. Unless Russia takes certain steps, a second set of penalties -- more stringent than this first round -- must follow, according to the law.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, CNN reported.The sanctions are mandated under the Chemical and Biological Weapons and Warfare Elimination Act of 1991.