(Adds Gates comments paragraphs 4-6, edits)
KABUL, Jan 10 (Reuters) - Afghanistan welcomed on Thursday 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.
In Brussels, NATO Secretary-General Jaap de Hoop Scheffer welcomed the U.S. plans but stressed that a number of European allies had in recent months also added forces there.
The Pentagon said on Wednesday 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 troops in Afghanistan.
Gates told reporters at the Pentagon on Thursday he had not yet decided to approve the plan and said he had concerns it would relieve the pressure on other NATO allies to provide more troops.
But he added: "I also am very concerned that we continue to be successful in Afghanistan, and that we continue to keep the Taliban on their back foot."
He said he expected to make a decision "pretty quickly."
Around half the current 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 Defense Ministry, said a U.S. troop increase 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.
However, "the Afghan National Army is the answer for the long-term security in Afghanistan to thwart internal and external threats to the country and to maintain the force balance," he said, adding that the number of trained soldiers would grow from 58,000 to 70,000 in the next two months.
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.
'CAN DO BETTER'
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.
Under the U.S. plan, most of the Marines would join British, Canadian and Dutch troops in southern Afghanistan, scene of the worst fighting. The Marines would be in place by April and stay for seven months.
NATO's de Hoop Scheffer pointed to recent smaller additions from countries including France, Slovakia, Hungary and Poland -- which on Wednesday announced it would add 400 troops and helicopters -- to its existing 1,200-strong contingent.
"You cannot say the allies are not active enough, because they are active. ... But I still think we can do better," he told reporters at an event in Brussels, noting persistent shortfalls in NATO's forces.
He also stressed the ultimate answer was not military but a long-term commitment to reconstruction and development.
"The solution for Afghanistan is not pouring in tens of thousands of forces," he said.
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.
De Hoop Scheffer argued that much of the good news in the country -- such as what he said was a doubling in the average Afghan personal income from 2001 -- was being overshadowed. (Additional reporting by Andrew Gray in Washington and Mark John in Brussels; writing by David Fox)
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