WASHINGTON (REUTERS) - Cyber attacks and cyber espionage have supplanted terrorism as the top threats to the United States in an annual "worldwide threat" assessment released on Tuesday by the US intelligence community.

However, in testimony prepared for a Senate Intelligence Committee hearing, James Clapper, the director of National Intelligence, played down the likelihood of catastrophic attacks on the United States by either cyber attackers or foreign or domestic militants in the immediate future.

In what has become an annual ritual, Clapper presented to the Senate panel a 34-page paper that ran through a wide variety of threats covered by US intelligence agencies.

These included high-profile issues such as North Korea's belligerence and the proliferation of nuclear weapons, as well as regional and economic issues like continuing instability in the wake of the Arab Spring uprisings.

Also covered was a potential transition in Cuba and what is predicted to be China's continuing domination of the world's supply of rare earth elements.

On two of the most volatile global crisis points, the US spy agencies' assessment was restrained.

While Iran is improving its expertise in technologies, including uranium enrichment and ballistic missiles, that could be used in a nuclear weapons program, the intelligence community does not believe Iran's leadership has decided to build a nuclear weapon and does not know if or when it might do so.

This assessment is consistent with a controversial 2007 finding, known as a National Intelligence Estimate, which declared Teheran had "halted its nuclear weapons program" in autumn 2003 and had not restarted it as of mid-2007, although it was keeping open the option of building nuclear weapons.

On Syria, US spy agencies assessed that the erosion of the government of President Bashar al-Assad's ability to defend itself "is accelerating."

Assad's forces have stopped insurgents from seizing cities such as Aleppo, Damascus and Homs, but the agencies say insurgents have been gaining strength in rural areas. This could ultimately lead to the establishment of a "more permanent base"for the rebels in Idlib province along the border with Turkey.