US Defense Secretary Robert Gates on Sunday said he is against a surge of American troops to Afghanistan beyond what has already been approved by President Barack Obama, as military power alone cannot solve the Afghan problem. "I would be a hard sell; there's no question about it," Mr. Gates told CNN in an interview when asked if he would support or oppose any further increase in troops to Afghanistan later this year, as being talked about at the Pentagon. "I have not made a secret of that, either publicly or in government meetings. I think we will have - between the American military commitment and our coalition partners, the ISAF partners, we will have about 100,000 troops in Afghanistan. That's only about 10,000 shy of what the Russians had. I think we need to think about that," he said. Expressing reservations about significant further commitments of American military to Afghanistan, beyond what the president approved in March, Mr. Gates said the Soviets, who were in the country with 110,000 - 120,000 troops, "did not care about civilian casualties and they could not win". "If there's ever an example that military power alone cannot be successful in Afghanistan, I think it was the Soviet experience," he said. Gates argued that it is absolutely critical for the Afghans to believe that this is their war.