The al Qaeda terror network is weakening and the embattled Afghan government is making modest strides, but cyber security threats are on the rise and Iranian nuclear aspirations remain a major peril.

These are among the main themes in the annual U.S. intelligence community's threat assessment, a sweeping 31-page document released Tuesday that touches on a range of issues across the globe.

"The United States no longer faces - as in the Cold War - one dominant threat," Director of National Intelligence James Clapper said in prepared testimony to the Senate Select Committee on Intelligence, which will meet on Tuesday to discuss the report.

He said "counterterrorism, counter-proliferation, cyber security and counter-intelligence are at the immediate forefront of our security concerns" and that the "multiplicity and interconnectedness of potential threats - and the actors behind them ... constitute our biggest challenge."

Al Qaeda - the terror network that attacked the United States on September 11, 2001 - "will continue to be a dangerous transnational force," but there have been strides, the report concludes.

The deaths of al Qaeda leader Osama bin Laden and top lieutenants under its new leader Ayman al-Zawahiri has made a dent in the Pakistan-based core of the group, the report said.

"These losses, combined with the long list of earlier losses since CT (counter-terror) operations intensified in 2008, lead us to assess that core al Qaeda ability to perform a variety of functions - including preserving leadership and conducting external operations - has weakened significantly," the report said.

"We judge that al Qaeda's losses are so substantial and its operating environment so restricted that a new group of leaders, even if they could be found, would have difficulty integrating into the organization and compensating for mounting losses."

They expect the leadership to have "sustained degradation, diminished cohesion and decreasing influence in the coming year." Al Qaeda will try to "execute smaller, simpler plots to demonstrate relevance."

The death of bin Laden and other leaders has affected their influence in the Arab uprisings, the report says.

"They probably will struggle to keep pace with events," the report said. "Rhetoric from Ayman al-Zawahiri, bin Laden's successor, has not resonated with the populations of countries experiencing protests."