By Phil Stewart and David Alexander

WASHINGTON (Reuters) - Russia, locked in a standoff with the West over Ukraine, would be unable to thwart a complete or partial U.S. withdrawal from Afghanistan even if it cut off access to Russian supply routes, a top U.S. general said on Wednesday.

Asked at a Senate hearing whether the United States could still get its equipment out of Afghanistan even if Russia cut off routes running through its territory, General Joseph Dunford, the top U.S. and NATO commander in the war effort, replied: "Yes."

"We've got resilience in the system and I'm not concerned at all about a loss of the Russian (routes in the) Northern Distribution Network," Dunford said, referring to the military's network of supply routes through Russia, the Caucasus and Central Asia.

U.S. lawmakers are preparing sanctions against Russia over its intervention in Ukraine, despite Moscow's warnings those sanctions would "boomerang" back on the United States. EU member states are also threatening sanctions, such as travel restrictions and asset freezes.

Dunford strongly warned Congress against withdrawing all American forces from the country this year - something he said would embolden al Qaeda, gradually erode the capabilities of Afghan forces and greatly undermine the rights of Afghan women.

"I think the plight of women would be pretty dire if we were to withdraw at the end of 2014," Dunford said.

More broadly, he predicted that if there were a complete U.S. withdrawal in 2014, "an emboldened al Qaeda will not only begin to physically reconstitute, but they will also psychologically exploit their perceived victory to boost recruitment, fundraising and morale."

U.S. President Barack Obama last month held out the threat of a complete withdrawal after outgoing President Hamid Karzai's refusal to sign a bilateral security pact.

The United States is waiting for Karzai's successor to be determined following the April elections before deciding whether to sign that pact.

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But Obama has warned the clock is ticking. The nearly 13-year-old war has largely fallen from view among the U.S. public.

Asked how long he could wait for a decision on whether to carry out an orderly withdrawal of all U.S. forces, Dunford said the risk would only start to become high in September.

Senator Lindsey Graham of South Carolina lamented to Dunford how poorly attended Wednesday's hearing on the war effort was, despite an upcoming decision on a U.S. troop presence he thought was critical to future U.S. security.

"One observation, the room is almost empty ... General, I remember when all these rows were full with people carrying bags and everybody was hanging on every word about Afghanistan," Graham said.

Dunford said he was comfortable with NATO planning to keep between 8,000 and 12,000 NATO troops in Afghanistan after 2014, along with thousands of additional U.S. forces focused on counter-terrorism operations against al Qaeda. There are now nearly 34,000 U.S. troops stationed in Afghanistan.

Senator Joe Manchin of West Virginia, however, sharply questioned why American forces should stay in Afghanistan after already fighting there for so many years.

"Can you honestly tell the American people ... that we should stay in Afghanistan?," he asked Dunford.

But Dunford stressed that if American forces leave, the only question was how quickly Afghan troops would see their ability to fight Taliban insurgents fade.

"The deterioration of the Afghan forces begins to happen fairly quickly in 2015," he said. "Units would run out of fuel, pay systems would not be completely operable, spare parts would not be available for vehicles and so we'd start to see decreased readiness in the Afghan security forces."

(Reporting by Phil Stewart, editing by G Crosse)