(CNN) -- President Obama's foreign policy agenda may have "run out of steam" and he must now take risks and provide effective leadership, former U.S. National Security Adviser Zbigniew Brzezinski said Friday.
In an interview with CNN's Christiane Amanpour, Brzezinski said Obama's foreign policy agenda is suffering from gridlock in Washington.
"I have the feeling that because of domestic problems, he has run out of steam, and I don't know really how determined he is to resume what he started doing so well, which is to engage the world constructively," Brzezinski said.
Brzezinski, who is now at the Center for Strategic and International Studies in Washington, said the only way to break the stalemate is for Obama to take the lead.
The president can show leadership, he said, by "persuasively going to the country directly, mobilizing the support, taking on some difficult foreign challenge, and prevailing."
Brzezinski cited Iran as an example of key challenges Obama ought to tackle.
Obama should not "abandon it prematurely," he said, noting the complexities of the internal Iranian situation could give the United States "room for maneuver, and perhaps some basis for expecting an eventual partial accommodation."
Brzezinski also cited the Israeli-Palestinian conflict as a key challenge because it "revolutionizes, radicalizes the Middle East, and maximizes the number of enemies the United States has."
Asked how he would grade the Obama administration's performance on Iran and the Middle East, he said, "Well, rhetorically, A; in terms of performance, B, B-minus."
Despite the United States' foreign policy problems, Brzezinski said, the nation has the resources to deal with new global security threats in cyberspace, outer space and on the high seas.
Brzezinski also commented on the newly published 2010 Quadrennial Defense Review, a legislatively mandated review of the U.S. Department of Defense strategy and priorities.
The review is meant "to assess the threats and challenges that the nation faces," and to "rebalance the department's strategies, capabilities and forces to address today's conflicts and tomorrow's threats," according to the Department of Defense.
Brzezinski warned even though the United States has highly sophisticated technology, it also has to be effective in global diplomacy, adding, "We have neglected that in the course of the last decade."
"I think we have to redefine the nature of the enemy," Brzezinski said, "the global security context in which we find ourselves is now fundamentally different."
Brzezinski, national security adviser during the Carter administration between 1977 and 1981, noted how the new threats differ from those of the Cold War.
"When I was in the White House, the threat was concentrated and very lethal," he said. "You know, the Soviet Union, in case of a central war with the United States, could kill roughly 80 million Americans in six hours."
Today, Brzezinski said, the United States has "a lot of threats, ranging from terrorists to rogue states to unpredictable events. And that makes the defense issue more complex, even though it is somewhat rather less lethal."
He cited the example of cyberattacks.
"Are these hackers, for example, from China working for the Chinese government or are they working for some private business? What are their motives?"
He said it is vital for the United States to have the capability not only to stop hacking, but to retaliate as well.