U.S. Vice President Joe Biden says the security situation in Pakistan worries him more than that of Iraq, Iran and Afghanistan.
In an interview with U.S. news network CNN Wednesday, Biden said Pakistan "has nuclear weapons that are able to be deployed" and "a real significant minority of radicalized population."
He added that Pakistan "is not a completely functional democracy."
Pakistan is key to the U.S. effort in neighboring Afghanistan, and Washington has supported Pakistan's offensive against militants in volatile border regions.
Biden also addressed concern that Iran's nuclear program is aimed at producing a weapon.
He said if Tehran gains weapons capabilities, it will put pressure on other countries in the region to do the same, naming Saudi Arabia, Turkey and Egypt.
The United States and other world powers are pushing for a fourth round of U.N. sanctions against Iran for its uranium enrichment activity - a process that could be used to build a weapon.
Iran insists its nuclear program is for peaceful purposes only.