WASHINGTON (AFP) - The United States on Friday urged both sides in Honduras's political showdown to return immediately to negotiations and forge a reconciliation government after the collapse of a US-brokered deal.

"We urge both sides to act in the best interests of the Honduran people and return to the table immediately to reach agreement on the formation of a unity government," State Department spokesman Ian Kelly said.

"We're disappointed with both sides," Kelly told reporters.

He said "we're disappointed that both sides are not following the very clear path laid out" in the Costa Rican accords aimed at restoring President Manuel Zelaya to power following his ouster in a June 28 coup.

Washington has tried for months to broker the deal, including shaping a widely hailed agreement last week.

The agreement had given Zelaya and interim leader Roberto Micheletti's camps until midnight on Thursday to establish a national unity government with members from both sides.

Although it did not require that Zelaya be reinstated to power, the pact said the decision should be left to Congress. A vote has yet to take place.

Shortly before midnight, Micheletti announced a unity government without including Zelaya ministers in the new cabinet. He did not name the ministers but left the door open for Zelaya ministers to later join the newly formed cabinet.

Zeyala had refused to present nominees for ministerial posts, as requested by Micheletti, unless he was first reinstated to "reverse the coup" that ousted him on June 28.

Zelaya said Friday that the deal to end the nation's political crisis had collapsed.

In a travel advisory, the State Department urged American citizens to "exercise caution" when traveling to Honduras, referring "to the current uncertain political and security situation" in the country.

It also urged them to defer "all non-essential travel" to the capital Tegucigalpa until further notice.