"I consider that talk of making fundamental changes to the country's development model is inappropriate -- inappropriate and not needed. About creating a so-called mobilised, or closed, economy," Medvedev said at an investment conference in the Black Sea resort of Sochi.
"Our country does not need such economy. No country needs such an economy."
"Our priorities remain unchanged. We will not change our course," said Medvedev, who served a four-year stint as president before ceding the Kremlin back to his mentor Vladimir Putin in 2012.
"We have the largest territory, we are a nuclear power, nearly 150 million people live in Russia, we are a territory with huge natural resources, a large market for goods, services and investment," said the 49-year-old prime minister.
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Russia is locked in a dramatic confrontation with the West over Ukraine, where Kremlin-backed separatists have been battling pro-Western Kiev forces since April.
Brussels and Washington have imposed several rounds of tough sanctions on Russia in a bid to cripple the country's economy and make Moscow change its course.
Many observers have expressed fears that instead of changing tack, Moscow will isolate itself further, and that its policies will become more unpredictable.
"What do our opponents want?" Medvedev said at the Sochi forum.
"To build a new world order which is based on uncompromising confrontation, or maybe simply close their eyes tight and pretend that Russia no longer exists? To isolate half the European continent from the rest of the world? This is impossible."
"No one can predict what effect the sanctions against Russia will have long-term on the global economy," he added.
"And what, has the development of our country stopped?"
Russia has banned most food imports from the West in response to its sanctions over Ukraine, which cut off the access of major banks and companies from capital markets and imposed travel bans and asset freezes on key allies of Putin.