The United States is warning Honduras that there will be a cascade of negative consequences for the Central American state if the coup that ousted elected President Manuel Zelaya on Sunday is not reversed. The Obama administration is backing mediation on the situation by the Organization of American States, the OAS.

Officials here say the removal of President Zelaya was unconstitutional, illegal and cannot be tolerated, and they say the country faces severe penalties from its hemispheric neighbors if the ousted leader is not restored.

A senior Obama administration official who briefed State Department reporters said if the coup is not reversed within 72 hours, as the regional body demanded late Tuesday, it would clearly mean the expulsion of Honduras from the OAS. He said that would trigger a cascade of events in which Honduras would find itself thrown out of many components of the inter-American system.

He said that given how interconnected the region is, Honduras can isolate, and hurt itself, in as he put it, some pretty dramatic ways.

The United States had tried to mediate in the simmering dispute that led to the coup, centering on what Mr. Zelaya's opponents saw as an effort to remain in power even though obligated by term limits to leave office in January.

But the Obama administration was quick to condemn his ouster by the military, and replacement with an interim government led by Roberto Micheletti, as an illegal coup.

The senior official said despite the complaints against Mr. Zelaya at home, the United States wants his unconditional return to power with all powers and privileges of office.

The official also commended Mr. Zelaya for what he said was his wise decision to postpone returning home to give time for OAS diplomacy, which State Department Spokesman Ian Kelly said earlier Wednesday is showing some progress.

"I think this is an important moment for the OAS, for the principles of the states of the Western Hemisphere, the democratic principles," said Ian Kelly. "And we believe the best way to work through this is through this OAS process. And we're seeing great progress through the OAS. And I think we should just give this process a chance to play out. The multi-lateral route is the way to go."

Unlike Spain and several other concerned countries, the United States has not recalled its ambassador from Tegucigalpa, stressing the need to keep channels of communication open with the Honduran people.

The Pentagon has cut off military contacts with Honduras but the State Department says it is still involved in a legal review of a cut-off of U.S. aid to Honduras, with officials saying privately that they hoped an early reversal of the coup would obviate the need for such a step.

An act of Congress requires a cut-off of most U.S. aid to countries where elected governments are unseated by the military.