Russia will end up retreating from Ukraine as the pressure from sanctions and Ukraine's well equipped military sap the country's will to fight, a former U.S. diplomat has predicted.

William Courtney, who served as Washington's ambassador to the ex-Soviet states of Kazakhstan and Georgia, told CGTN that the loss of life would simply become too steep to bear.

"The costs are going up. NATO's now saying that up to 15,000 Russian soldiers have died in the first two to four weeks of fighting. That's twice as many U.S. soldiers that died in 20 years of fighting in Iraq and Afghanistan combined. So this is going to be hard for Russia to prosecute successfully. I think in the end, we're talking about Russia making some kind of a retreat," he said.

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Even though the West has refused to enforce a no-fly zone above Ukraine, the sophisticated weapons supplied to Kyiv, combined with years of training from NATO instructors, has been effective in restricting Russian air power, he said.

He also pointed out that the durability of sanctions following Russia exercising its claim over Crimea, had shown that the economic stranglehold will not be released.

Another analyst, Pavel Lubin from think tank Riddle, said that the Russian campaign had been undermined by flawed planning.

The security services, rather than the military, had taken the lead in the run up to the conflict and had failed to appreciate the strength of Ukraine's individuals and the population's will to fight, he said. In addition, poorly trained and educated soldiers and officers unaccustomed at managing battlefield situations have weakened the army's fighting capacity, he added.