The interim government of Honduras has said it will not allow a high-level delegation from the Organisation of American States to visit for talks.
It said OAS chief Jose Miguel Insulza would not be an impartial observer.
The delegation was hoping the Honduran government would accept a plan under which ousted President Manuel Zelaya would return and elections be held.
Mr Zelaya was sent into exile after a coup in June amid a power struggle over his plans for constitutional change.
His critics said the move was aimed at removing the current one-term limit on serving as president, and paving the way for his re-election.
Following the army-led coup on 28 June, the speaker of Congress, Roberto Micheletti – constitutionally second in line to the presidency – was sworn in as interim leader.
The OAS has demanded Mr Zelaya’s immediate reinstatement.
It suspended Honduras’ membership after the interim government failed to abide by a deadline to restore Mr Zelaya to power.
‘Damage to democracy’
Mr Insulza was to be accompanied on the visit to Tegucigalpa on Tuesday by the foreign ministers of Argentina, Canada, Costa Rica, Jamaica, Mexico and the Dominican Republic.
"Unfortunately, Insulza’s intransigence and his insistence on including himself in the delegation… has made it impossible to allow this visit in the scheduled date"
Honduran Foreign Ministry
But on Sunday, the Honduran foreign ministry announced that it would turn back the group because of the presence of the OAS secretary-general.
It also said other unnamed countries it considered more sympathetic were not represented in the delegation.
"Unfortunately, Insulza’s intransigence and his insistence on including himself in the delegation and to exclude foreign ministers of member states that… are open to reconsidering our case has made it impossible to allow this visit in the scheduled date," it said.
But the foreign ministry said it was willing to reschedule the visit as long as the delegation does not include Mr Insulza, whose "lack of objectivity, impartiality and professionalism" in his role had "resulted in serious damage to democracy".
The OAS hopes Mr Micheletti can be persuaded to accept a detailed plan proposed by the Costa Rican President, Oscar Arias.
Under this, Mr Zelaya would return to serve out his presidency and a government of national reconciliation would be set up. There would be an amnesty for political crimes committed during the crisis, and presidential elections would be brought forward to 28 October.
But the interim government says his return to power is an impossibility. Mr Zelaya says it is "non-negotiable".
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