Obama unveils cyber-security action plan

US President Barack Obama unveiled a cybersecurity "national action plan" on Tuesday as his intelligence chief warned of growing risks from new technologies that open more doors to hackers.

"More and more, keeping America safe is not just about more tanks or more airplanes," Obama told reporters at the White House.

"We also have to bolster our security online. As we've seen in the past few years, and just in the past few days, cyber threats pose a danger not only to our national security but our economic security."

US intelligence chief James Clapper underscored those risks at a Senate hearing, pointing out that wider adoption of connected devices and new systems that rely on artificial intelligence can open up doors to hackers.

Clapper named Russia, China, Iran and North Korea as "leading threat actors" which pose risks for US security, and said these risks are growing as technology evolves and moves into new devices.

Meanwhile, the US Supreme Court on Tuesday put on hold a sweeping plan to reduce greenhouse gas emissions from coal-fueled power plants, dealing a significant blow to President Barack Obama's efforts to rein in climate change.

A coalition of 27 US states -- most of them run by Obama's Republican adversaries -- is suing in a lower court to halt Obama's Clean Power Plan, and petitioned the Supreme Court to suspend its implementation until the case is resolved.

The White House said it was disappointed in the ruling, but convinced the ambitious plan to slash US emissions was based on a strong legal foundation, and would prevail.

The ruling halts the rollout of rules that require the power sector's carbon dioxide emissions to be slashed by at least 32 percent compared to 2005 levels by the year 2030.