Clapper's warnings were contained in the 2013 Worldwide Threat Assessment presented at a hearing of the U.S. Senate Select Committee on Intelligence Tuesday.
"I will say that in my almost 50 years of intelligence, I do not recall a period in which we confronted -- we confront a more diverse array of threats, crises, and challenges around the world ... . This year's threat assessment illustrates how dramatically the world and our threat environment is changing," Clapper said at the hearing.
He said the threats are growing more interconnected, where events which at first seem local and irrelevant could quickly set off transnational disruptions affecting U.S. national interests.
"It's a world in which our definition of war now includes a soft version. We can add cyber and financial to the list of weapons being used against us. And such attacks can be deniable and non-attributable," he said
"So when it comes to distinct threat areas, our statement this year leads with cyber, and it's hard to overemphasize its significance. Increasingly state and non-state actors are gaining and using -- using cyber expertise."
He said such actors apply cyber techniques and capabilities to achieve strategic objectives by gathering sensitive information from public and private sector entities, controlling the content and flow of information and challenging perceived adversaries in cyber space.
"These capabilities put all sectors of our county -- country at risk from government and private networks to critical infrastructures," Clapper said.
The director said there are indications some terrorist groups are interested in developing offensive cyber capabilities even as cyber criminals use a growing black market to sell cyber tools.
Others affecting national security include those relating to natural resources and food security.
"Terrorists, militants and international crime groups are certain to use declining local food security to gain legitimacy and undermine government authority," Clapper said.
"Intentional introduction of a livestock or plant disease could be a greater threat to the United States and the global food system than a direct attack on food supplies intended to kill humans."
As for terrorism, Clapper said the threat from core al-Qaida and the potential for a massive coordinated attack on the United States has diminished, but the global Jihadist movement is a more diversified, decentralized and persistent threat.
"Lone wolves, domestic extremists and Jihadist inspired groups remain determined to attack western interests as they've done most recently in Libya and Algeria," he said.
Weapons of mass destruction development and proliferation are other major threats to U.S. interest, he said, citing the examples of North Korea and Iran.
China, Clapper said, is supplementing its more advanced military capabilities by bolstering maritime law enforcement to support its claims in the South and East China Seas. "It continues its military buildup and its aggressive information stealing campaigns," he said.