Moscow: Russia has pulled out of a popular US-funded student exchange programme, accusing its organisers of violating the rules by allowing a teenager to stay behind in the United States.
"One of the reasons is a crude violation by the receiving side of its obligation to unconditional return the students who arrived from Russia," the Russian children`s ombudsman Pavel Astakhov said on Twitter on Wednesday.
"A Russian teen stayed behind in the United States," he wrote, without giving further details.
Over 8,000 Russian high school students used the 2015-2016 Future Leaders Exchange (FLEX), which US Ambassador to Russia John F. Tefft described as the "largest U.S.-Russian educational exchange program".
"We deeply regret this decision by the Russian government to end a program that for 21 years has built deep and strong connections between the people of Russia and the United States," he said in a statement on Tuesday.
Following the collapse of the Soviet Union, the US government and non-government organisations sponsored a number of exchange programmes for young Russians in a bid to improve ties with the former Cold War enemy.
Many of the Russian students chose not to return.
"There is nothing bad in international exchange programmes for pupils, students and specialists per se but only until rules get violated," said Astakhov on Twitter.
In 2012, President Vladimir Putin banned the adoption of Russian children by American families. Activists decried the move, saying it lessened the chances of disabled orphans finding a home.
The ban came in retaliation for a US law punishing Russian officials implicated in the 2009 prison death of whistle-blowing attorney Sergei Magnitsky.
Tensions between Moscow and Washington have dramatically intensified over the Ukraine crisis, with the United States introducing several rounds of sanctions against Russia over its support for separatists in the ex-Soviet state.