Al-Qaeda represents the most serious threat to US interests, the new US intelligence chief has said.
McConnell says al-Qaeda is still trying to acquire WMDs
Michael McConnell told a congressional panel the Lebanese militant group Hezbollah also posed a grave threat.
He also said Iran and North Korea were of most concern to the US because there was a risk they could spread weapons of mass destruction (WMDs).
Mr McConnell, who became head of the 16 US spy agencies this year, said Iraq was "moving in a negative direction".
The retired admiral told the Senate Armed Services Committee that al-Qaeda elements were still trying to acquire weapons of mass destruction.
"They continue to plot attacks against the homeland and other targets with the aim of inflicting mass casualties. Indeed, al-Qaeda, along with other terrorist groups, continues to seek chemical, biological, radiological and nuclear weapons or materials," he said.
"Al-Qaeda is also forging stronger operational connections that radiate outward from their camps in Pakistan to affiliated groups and networks throughout the Middle East, North Africa and Europe."
Mr McConnell said Iran and North Korea still posed a threat of nuclear proliferation, despite the nuclear agreement recently signed with North Korea.
"We assess that Iran seeks to develop nuclear weapons and has shown greater interest in drawing out the negotiations rather than reaching an acceptable diplomatic solution," he said.
"This is a very dangerous situation as a nuclear Iran could prompt destabilising counter-moves by other states in this volatile region.
"While our information is incomplete, we estimate that Iran could produce a nuclear weapon by early to mid next decade," he added.
Beyond that, Iran was also a concern to the US because of its alleged activities in Iraq.
Mr McConnell acknowledged that the US had no proof that the Iranian leadership was directly involved in supplying Iraqi Shia insurgents with weapons, but he said his assessment was that there was a "probable" link.
Regarding North Korea, he said "open questions" remained about the North's intentions, but added that "so far, the indications were in a positive direction".