Kara-Murza told a US Senate foreign relations budgetary committee on Wednesday that leaders of Western democracies had for too long "just ignored" Putin's actions.

His testimony followed a letter Kara-Murza sent in January to the Senate, in which he asserted that Putin's three-term rule had seen the "dismantlement" of nascent democratic institutions that emerged when the Soviet Union collapsed.

A West that continued to signal "weakness" would be an invitation to Putin's administration to carry on, when instead it was "vital" that the United States support the work of Russian pro-democracy movements, he said.

"This is not only about money. Much more importantly, it's about the message the US sends to Russia's civil society," said the vice chairman of Open Russia, a foundation run by exiled Kremlin critic Mikhail Khodorkovsky.

"Do you choose to engage or to turn away?" Kara-Murza asked senators, and urged them to continue to apply sanctions on some 40 Russians accused of serious human rights violations.

Poision substance unidentified

The Russian opposition politician, allied with Boris Nemtsov, who was shot dead close to the Kremlin in 2015, has often been chastised by Russian state media for lobbying in the West.

He told US lawmakers Wednesday that his departure from Russia last week for treatment followed poisoning by a substance that his doctors still had not been able to identify.

"Sometimes there are near misses" in Russian political murders, "and one happens to be sitting before you," Kara-Murza told the Senate panel.

Boost funding, urges Graham

Senator Lindsey Graham, one of the few congressional Republicans to openly criticize President Donald Trump's past calls for closer ties with Russia, said he wanted Congress to establish a "counter-Russia account to help frontline states and organizations who are fighting back against Putin's regime."

Graham said it was in American taxpayers' interests that "we push back against Putin's efforts to dismantle democracy throughout the world."

ipj/bw (AP, AFP)