By Hamid Shalizi

KABUL, Jan 10 (Reuters) - Afghanistan gave a welcome on Thursday to U.S. plans to send an extra 3,000 troops to fight the Taliban insurgency, but Washington's move highlights divisions between Western allies over how much to commit to the country.

The Pentagon said on Wednesday that U.S. Defense Secretary Robert Gates was considering sending an additional 3,000 Marines to thwart any Taliban spring offensive, bringing to around 30,000 the number of American servicemen and women in Afghanistan.

Around half the U.S. contingent serves in a 40,000-strong NATO-led International Security and Assistance Force (ISAF), while the rest conduct missions ranging from counter-terrorism to reconstruction to training Afghan troops.

Zahir Azimi, a spokesman for Afghanistan's Defence Ministry, said the increase in troop numbers would help anti-insurgency operations as the new national army continued to grow.

"As we are in the fight together with the international community, the deployment of additional troops to Afghanistan is considered necessary in the current situation," he said.

"(But) The Afghan National Army is the answer for the long-term security in Afghanistan to thwart internal and external threat to the country and to maintain the force balance."

Washington, stretched by last year's troop surge in Iraq, has for months been trying in vain to persuade NATO allies to commit more combat troops to Afghanistan to take up the slack.

But European governments have been reluctant to increase their operations here and, wary of a big dip in domestic public support for their continued presence, have been scaling back.

"Our allies are not in a position to provide them (extra troops) so we are now looking at perhaps carrying a bit of that additional load," Pentagon press secretary Geoff Morrell said in Washington.

He said most of the Marines would go to southern Afghanistan, where British, Canadian and Dutch troops have done much of the fighting.

While NATO says it thwarted last year's attempted Taliban spring offensive, overall violence is up 27 percent over a year ago and has risen by 60 percent in the southern province of Helmand, the U.S. military said last month.

"The idea is to get this in place to prevent, as we did last spring, another attempt by the Taliban to come back," Morrell told reporters. "The timing is that they would be in place by April. This is a one-time seven-month deployment."

Azimi said the new Afghan National army currently numbered 58,000 trained officers and soldiers and would reach 70,000 in the next two months. (Reporting by Hamid Shalizi; additional reporting by Andrew Gray in WASHINGTON; writing by David Fox; editing by Roger Crabb)

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