U.S. Secretary of State John Kerry said on Thursday that an agreement reached after high level talks among representatives from Russia, Ukraine, the U.S. and the EU on the crisis in Ukraine called for all sides to "refrain from the use of violence." (Photo: Getty Images)

US SECRETARY of State John Kerry has attested to the massively complex challenges Washington faces in Ukraine, Russia, Iran and the Middle East, declaring “it was easier” during the Cold War.

In a candid moment during a State Department speech, the top US diplomat said changing global power dynamics made a quaint memory of the early East-West stalemate, when American children would “crouch under our desks at school and practice” safety steps for a possible nuclear attack.

“During the Cold War... it was easier than it is today - simpler is maybe a way to put it,” Kerry told aid and development experts.

“The choices were less varied, less complicated, more stark, more clear: Communism, democracy, West, East, the Iron Curtain.”

He said “multiple emerging powers”, unleashed forces like radical Islam, and “too many failed states” have dramatically complicated the landscape, requiring a form of diplomatic precision that was not absolutely necessary decades ago.

In the post-war 1950s and 1960s, Kerry said, “we could make really bad decisions and still win, because we were pretty much the sole dominant economic and military power around”.

“It’s not true any more.”

Today, as Kerry juggles a handful of critical crises and diplomatic impasses that would vex any world leader, his skills are being put to the test particularly in the tense dispute between Russia and Ukraine over Kremlin aggression.

But he said there were global bright spots too, including efforts to finalise nuclear negotiations with Iran.

“Yes, we’re fighting some complicated issues in Ukraine. Yes we’ve got struggles in Syria and Middle East and places,” he said.

“Look at huge vast parts of the world where we are able to maintain the calm, able to navigate and thread the needle.”