Al Qaeda [Images] has increased its operational reach through partnerships with regional terrorist groups while continuing to plan and direct attacks from its safe haven in Pakistan's frontier provinces, top US intelligence officials say.

Addressing the Senate Armed Services Committee at a hearing on National Security Threats, the intelligence chiefs also said Al Qaeda remains a "pre-eminent" threat to the US despite its recent losses as the group retained or regenerated key elements of its capability, including the top leadership.

"Al Qaeda has extended its operational reach through partnerships and mergers with compatible regional terrorist groups, including a continued effort to expand into Africa. Al Qaeda maintains its desire to possess weapons of mass destruction," the Director of Defence Intelligence Agency, Lt Gen Michael Maples, said.

"We believe Al Qaeda has expanded its support to the Afghan insurgency," he said, adding the group continues to "plan, support and direct transnational attacks from its de facto safe haven" in Pakistan's largely ungoverned frontier provinces.

Maples also said Al Qaeda presents an "increased threat" to Pakistan.

National Intelligence Director Michael McConnell said Al Qaeda remains the "pre-eminent terrorist threat" to the US as "despite our successes, the group has retained or regenerated key elements of its capability, including top leadership, operational middle level lieutenants, and de facto safe haven."

McConnell praised Pakistani authorities in the 'war against terror', saying Islamabad "helped us more than any other nation" in counter-terrorism operations.

Lt Gen Michael Maples said Pakistani military operations in the Federally Administered Tribal Areas (FATA) have had "limited effect" on Al Qaeda.

Regarding the threat to the safety of the country's nuclear arsenal, Gen Maples maintained the US had "confidence" in Pakistan's ability to safeguard its nuclear weapons.

He also said Al Qaeda is interested in recruiting operatives who can travel easily and without drawing scrutiny from security services.

"As such, Europe could be used as a platform from which to launch attacks against the United States," he said.