Honduras has been fighting diplomatic isolation since last year after an election that replaced Zelaya and put Porfirio Lobo in power. Lobo's election was condemned as illegitimate by several Latin American countries.
The United States is among a few countries that recognized Lobo's presidency as a tough compromise in a last-minute diplomatic bid to resolve a crisis that was created when Zelaya was deposed by the Honduran military in June 2009 upon orders from the country's Supreme Court.
The court ordered Zelaya's ouster after he tried to change the constitution to remain in power. The United States and European Union suspended aid to Honduras to demonstrate displeasure with the coup. U.S. officials campaigned for months afterward to find a solution that could keep Honduras democratic.
The impoverished, violence-ridden country was ostracized at the Organization of American States, which also poured resources into finding a democratic solution.
The ouster of Zelaya deteriorated into a polarized political confrontation in which the coup leaders allegedly took active part. The final toll from pro-Zelaya riots, pro-coup repression and economic and political chaos is yet to be determined.
Reconciliation between warring factions has progressed slowly as the hard-pressed Honduran economy has sunk lower into recession and the country's 8.2 million citizens have been pushed further into poverty.
This week's fragile accord, brokered by Colombia and Venezuela and aiming to bring together Lobo and Zelaya for an amicable resolution, will be tested when a final signing takes place next week. When formalized, the agreement will open the way for Honduras to resume its seat at the OAS in Washington.
The country's OAS membership is seen as an essential step toward diplomatic recognition for Lobo's presidency in Latin America and beyond. OAS insists Zelaya should be able to return to Honduras without fear of prosecution before it can restore the country's membership.
Zelaya and Lobo have already had informal talks on sinking their differences after Colombia and Venezuela brought them together in the Colombian port city of Cartagena and encouraged them to initial an interim accord.
The agreement also gives guarantees that Zelaya and his former aides can take part in the political process before the next presidential elections.
Lobo has been recognized by several Central American states friendly to Washington but not yet by South American states that saw the coup as an unacceptable reminder of Latin America's turbulent history of unconstitutional government takeovers.
The United States condemned the coup but helped broker the elections that brought Lobo to power. Washington argues Lobo's government deserves a chance as it has shown sufficient commitment to democracy.
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