Read the State Department report, "Country Reports on Terrorism"

Washington (CNN) -- Despite some setbacks, al Qaeda's core leadership in Pakistan remains the biggest threat to the United States, and the group continues to expand and strengthen worldwide, according to a new State Department report.

Last year, al Qaeda's "core in Pakistan remained the most formidable terrorist organization targeting the U.S. homeland," says the report, "Country Reports on Terrorism."

"It has proven to be an adaptable and resilient terrorist group whose desire to attack the United States and U.S. interests abroad remains strong," the report says.

The annual report covers the terrorism landscape in countries around the world and governments' efforts to combat it.

Al Qaeda suffered leadership loses and faced pressure stemming from the Pakistani military campaign in the tribal areas, which limited the group's ability to carry out spectacular attacks. However, according to the report, al Qaeda was "actively engaged in operational plotting" against the United States and continued to recruit, train and deploy operatives, including some from Western Europe and the United States.

Al Qaeda also sought to expand its operational capabilities by partnering with other terrorist groups worldwide, the report says.

The overall picture of terrorism last year underscores new threats in Somalia and Yemen, where insurgents have gained strongholds in vast, lawless areas.

Al Qaeda affiliates in Africa -- including al Qaeda in the Islamic Maghreb and Al-Shabaab in Somalia -- are among al Qaeda's "most active" worldwide, the report says. Al-Shabaab, it says, presents a "serious terrorist threat to American and allied interests throughout the Horn of Africa."

Read about indictments against U.S. citizens linked to Al-Shabaab

The report also says groups such as al Qaeda in the Islamic Maghreb and al Qaeda in the Arabian Peninsula pose a significant threat to U.S. interests. It cited Umar Farouk AbdulMutallab, who attempted to blow himself up while on a flight into Detroit, Michigan, and admitted that he was trained by the Arabian Peninsula group in Yemen.

Weak efforts by the government in Yemen have allowed the group to use the country as a safe haven for planning future attacks, the State Department report says.

In addition to Yemen and Somalia, the report also singles out the tribal areas of Pakistan as a place where militants find safe haven. It says al Qaeda and other groups, such as the Haqqani Network, used the Federally Administered Tribal Areas in northwest Pakistan to "launch attacks in Afghanistan, plan operations worldwide, train, recruit, and disseminate propaganda," while the Pakistani Taliban also used that region to plan attacks against the civilian and military targets across Pakistan.

Lashkar-e-Tayyiba also found safe haven in Pakistan, enabling it to plan regional operations from within the country, according to the report.

It says Lashkar-e-Tayyiba "is an extremely capable terrorist organization with a sophisticated regional network. It continued to view American interests as legitimate targets."

Last year found more cases of Americans becoming operatives for terrorist organizations and advocates for violent extremists, most notably Anwar al-Awlaqi, whom the report called an "influential voice of Islamist radicalism among English-speaking extremists."

It noted that Nidal Hasan, the suspect in the Fort Hood, Texas, shooting in November 2009, sought out al-Awlaqi for guidance, and AbdulMutallab visited him at least twice in Yemen.

The report calls Iran the "foremost state sponsor of terrorism" for its support of Hezbollah, Hamas and other terrorist groups, which it says "had a direct impact on international efforts to promote peace, threatened economic stability in the [Persian] Gulf, jeopardized the tenuous peace in southern Lebanon, and undermined the growth of democracy."

It also says Syria helped Iran arm Hezbollah and provides safe haven to Hamas and other terrorist groups.

The threat environment of the future, the report says, could be shaped by a growing youth population in South Asia and the Middle East, as well as Europe, which has faced challenges integrating an increased number of Muslim immigrants.

Cyberspace will continue to be a focus of U.S. counterterrorism efforts, the report says.

Terrorists have been increasingly interested in using the Internet to target the United States, but to date have been able only to transfer funds and spread propaganda.

However, the report says, al Qaeda "continued its efforts to encourage key regional affiliates and jihadist networks to pursue a global agenda, using both the Internet as a means to distribute propaganda and telecommunications infrastructure to plan attacks and coordinate movements. Going forward, this will be an area of continued focus for the United States."