U.S. Defense Secretary Robert Gates warns that terrorist groups that have found a safe haven in Pakistan are the greatest threat to stability in neighboring Afghanistan and represent a significant danger to the United States. But Gates cautioned against a rapid military expansion in Afghanistan, even though the top U.S. military commander there has asked for thousands of additional troops. VOA correspondent Meredith Buel reports from Washington.

US Defense Secretary Robert Gates

Gates told members of the Senate Armed Services Committee Tuesday that the United States faces committed enemies in the tribal areas of Pakistan and until those safe havens are removed, insecurity and violence will persist. "If you asked me today, after the successes that we have had against al-Qaida in Iraq where the greatest threat to the homeland lies, I would tell you it is in western Pakistan," he said.

U.S. officials say al-Qaida and Taliban fighters use Pakistan's tribal region to launch attacks inside Afghanistan, and to plot against the United States and other western countries.

The senior U.S. military leader in Afghanistan, General David McKiernan, said last week he needs at least 10,000 more troops to fight the insurgents, in addition to another U.S. combat brigade that is scheduled to arrive in January.

But Secretary Gates warns against a swift U.S. military expansion in Afghanistan. "Are we better off channeling resources into building and expanding the size of the Afghan national army as quickly as possible as opposed to a much larger western footprint in a country that has never been hospitable to foreigners, regardless of why they are there," he said.

Gates says the United States will not have enough forces available until next year to meet a request by the North Atlantic Treaty Organization for three additional combat brigades in Afghanistan.

The defense secretary says extra forces alone will not solve the problem. "Security is just one aspect of the campaign, alongside development and governance.  We must maintain momentum, keep the international community engaged and develop the capacity of the Afghan government," he said.

In Iraq, Gates says overall violence is down 80 percent.  But he cautions against using the improvement in security as a reason to more quickly withdraw U.S. soldiers from the country. "I worry that the great progress our troops and the Iraqis have made has the potential to override a measure of caution born of uncertainty.  Our military commanders do not yet believe our gains are necessarily enduring.  And they believe that there are still many challenges and the potential for reversals in the future," he said.

Earlier this month, U.S. President George Bush announced that about 8,000 troops are being withdrawn from Iraq and that more American forces are being sent to Afghanistan.