MOSCOW - Since he took over Crimea, President Vladimir V. Putin has seen his popularity soar and his opposition fall silent. So when Vice President Biden told Russia to defuse tensions in Ukraine, Putin had few reasons to listen.

Emboldened by the national euphoria over the annexation of Crimea, Putin has moved against the few remaining critical voices in Russia and further neutered the news media. On Tuesday, a court cleared the way for sending his most vocal critic to prison.

Opposition leader Alexei Navalny was found guilty of slandering a lawmaker and fined the equivalent of $8,400. As a result, he may be jailed during a trial in a second case that starts Thursday. If found guilty, he could be sent to prison.

Putin has begun to cast his critics as "national traitors," an intimation that anyone who opposes the Kremlin is serving the interests of the West.

The travel bans and asset freezes imposed on Russian officials by the U.S. and European Union have been greeted publicly by bravado and ridicule in Moscow, with those targeted proclaiming themselves proud to have made the sanctions list. But the sanctions have hurt Russia's economy by spooking investors and driving up inflation as the ruble has lost value.

The U.S. and EU have said they will broaden the list and impose more punishment against Russia's banking and energy sectors if Moscow fails to follow through on the provisions of an international agreement on Ukraine reached last week in Geneva.

On Tuesday, Putin said that Russia should step up its presence in the Arctic and challenge other nations in exploring the world's largest untapped natural reserves.

Russia's ambitions in the Arctic have for some time been raising eyebrows among other states vying for a presence there, but the annexation of Crimea is likely to put its Arctic plans under greater scrutiny.

"Over decades, step by step, Russia has built up, strengthened its positions in the Arctic," Putin told a meeting of his Security Council in the Kremlin. "And our goal is not only to regain them, but also to qualitatively strengthen them."

Last year Putin ordered the reopening of a Soviet-era Arctic military base in the Novosibirsk Islands, two decades after it was abandoned.

"We must take additional measures not to fall behind our partners, to keep our influence in the region and in some aspects be ahead of our partners," he said.

This article contains information from Reuters news service.