Washington: Iran is feeling the pinch of mounting international sanctions particularly on its oil sector the US said on Friday, amid Tehran's threat to close down a key waterway in the Persian Gulf.

"We have seen quite a bit of irrational behaviour from Iran recently. One can only guess that the international sanctions are beginning to feel the pinch and that the ratcheting up of pressure, particularly on their oil sector, is pinching in a way that is causing them to lash out," State Department spokesperson Victoria Nuland said.

Earlier in the day, the US said it is in talks with major oil producing countries on contingency plans following the Iranian threat that it could close the strategic Strait of Hormuz.

The strait is just 34 miles wide, and about 20 percent of the world's oil shipments pass through.

"The United States maintains a regular, full and robust dialogue with significant energy producing and consuming countries on various aspects of the oil markets, including contingency plans in the event of disruptions to those markets," the State Department said in a statement on Thursday.

However, it declined to comment on the specifics of these discussions; which has been started by the US after the Iranian threat.

The United States has warned Iran from not doing so stating that such a move would not be tolerated.

The strong American statement came after the Iranians vice president warned that his country could block the strait if sanctions are imposed on its exports of crude oil.