Joseph Stone, 36, who worked for the Organisation for Security and Cooperation in Europe (OSCE), was killed when the armoured vehicle in which he was travelling hit a landmine.
The OSCE monitoring mission is made up of unarmed civilians from various countries who observe and report on activity in Ukraine and help foster dialogue among the parties fighting each other.
Russia has now accused the US of making wild claims and using Mr Stone’s death to push for a greater NATO military presence along the Russian border.
A US government body known as the Helsinki Commission discussed the incident at hearing called The Growing Russian Military Threat in Europe: Assessing and Addressing the Challenge.
A US commission has accused Russia of threatening to use tactical nuclear weapons
OCSE observer Joseph Stone was killed in Ukraine
Moscow threatens to use tactical nuclear weapons against other countries
Commission co-chairman Chris Smith told the hearing: “If it was not for Russia’s aggression and a plethora of challenges that they face from the very beginning of that deployment, there would have been no death of that wonderful young man and so many others.”
Mr Smith said Russia had grown into a formidable force which was threatening the entire OSCE region and “recklessly endangering the lives of millions.”
He went on to claim: “Moscow threatens to use tactical nuclear weapons against other countries.”
The allegations have ruffled feathers in Russia which has accused the commission of producing the “wildest claims to push for a military buildup in Ukraine”.
Tensions remain high in Ukraine
The pro-Moscow Russia Today said the Helsinki Commission had “pinned the blame” for Mr Stone’s death on Moscow and was using it to call for more arms and troops to be sent to the Russian border.
It said: “The New Jersey representative fell short of specifying what countries exactly are facing such threats and who has ever voiced them.
“While statements on the ‘Russian aggression’ are often uttered by US politicians, the veracity of some of the claims put forward at the hearing would not disappoint even the staunchest anti-Russian hawks.
“The investigative team has not yet come forward with any conclusions concerning Mr Stone’s death but the death of the Special Monitoring Mission (SMM) member has already been used to fuel anti-Russia rhetoric in western media.”
Ukrainian children are evacuated from the 'front line'
EXPLOSIVE: American tanks FIRE towards Russia
Fri, January 20, 2017
Heavily-armed US military personnel were rushed to Poland’s border with Russia to warn Vladimir Putin against another Ukrainian-style land grab.
US Army/Cover Images
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A round is fired from an M1A2 Main Battle Tank belonging to 1st Battalion, 68th Armor Regiment, 3rd Armored Brigade Combat Team, 4th Infantry Division during the first Live Fire Accuracy Screening Tests at Presidential Range in Swietozow, Poland
It quoted Russian President Vladimir Putin who said: “Russia never interferes, either in political life or in the political processes of other countries and would like to see other countries following suit.
“Unfortunately, what we see is precisely the opposite. We have seen attempts to interfere in internal political processes in Russia for a very long time.”