The Russian military has lost more than 10% of the combat force that President Vladimir Putin sent to invade Ukraine, a senior Pentagon official said, writes USA TODAY.

“The Russian combat force has dipped slightly below 90% for the first time in a war that began less than a month ago. Not all of the more than 150,000 Russian troops in and around Ukraine are combat troops; many provide support functions”, - said the official, who spoke on condition of anonymity to describe intelligence assessments.

The official described Ukrainian resistance as quick and nimble – and for the first time in the war seeking to retake ground from the Russians.