LAS MANOS, Honduras - Ousted Honduran President Manuel Zelaya briefly stepped across the border from Nicaragua to Honduras on Friday, in a symbolic move almost a month after soldiers sent him into exile.

Clashes between police and Zelaya supporters erupted on the Honduran side of the border as Zelaya arrived just meters away in Nicaragua ahead of an expected showdown in his second attempt to return to power.

Surrounded by a throng of supporters and media, Zelaya, wearing a leather waistcoat and his traditional cowboy hat, stepped into Honduras and shortly afterwards moved back into Nicaragua.

Honduran troops expelled Zelaya from the country at gunpoint on June 28 in a move supported by the Central American country's courts and legislature as he sought to hold a referendum on changing the constitution.

Zelaya arrived at the Las Manos border crossing point in Nicaragua in a jeep at around midday (1800 GMT) as anti-riot police fired tear gas on hundreds of his supporters massed on the other side.

Shortly beforehand, the Honduran government imposed an 18-hour curfew in border areas, while the army closed the border with Nicaragua and said it would not guarantee Zelaya's safety.

"We can't be responsible for the security of people who, by inciting generalized violence in the country, may be subject to attacks even from their own supporters who may have the sole aim of turning them into martyrs," an army statement said.

While international television broadcast Zelaya's return, Honduran channels made no mention of it, showing regular programs.

In Nicaragua, Zelaya's foreign minister, traveling with him, said the ousted leader would meet with social groups to decide how to proceed with his entry into Honduras, where de facto leaders have ordered his capture.

Zelaya said earlier he was considered crossing by land or air.

"We have planes and helicopters to go today to (cross) the border to Honduras," Zelaya said in Nicaragua.

Zelaya announced he would return home after talks with the interim government, brokered by Costa Rican President Oscar Arias, this week collapsed.

In a first attempt, on July 5, he tried to fly into Tegucigalpa airport, but was blocked by military units deployed on the runway, while on the ground at least one of his supporters died in clashes with troops.

Regional powers, including the United States, have backed Zelaya's quest to return constitutional order in Honduras, but urged him not to come back for fear of prompting bloodshed in a country some say is on the brink of civil war.

Zelaya was traveling in a 50-vehicle caravan alongside his Foreign Minister Patricia Rodas; Venezuelan Foreign Minister Nicolas Maduro, and Nicaraguan former rebel leader Eden Pastora.

Leaders across the region were meanwhile in rhetorical high gear, with the leftist alliance of Venezuela, Cuba, Bolivia, Nicaragua and Ecuador generally blaming the United States for the deadlock.

Brazil's President Luiz Inacio Lula da Silva told a summit in Paraguay Friday the Honduran coup could "not be tolerated, and we cannot back down. We condemn the interruption of democracy in Honduras."

The Mercosur summit said in a final declaration that it did not recognize the de facto government of Honduras and considered its actions invalid.