Salvador Sanabria, a rebel representative in Washington, defended Mr. de Soto as "one of the most active diplomats" trying to bring peace to his country.
"We would like to hope we are closer to peace but it is too early to tell," said Tesfai Ghermazien, an Eritrean rebel representative in Washington.
In Guatemala, the accord has led the Government to meet with leftist rebel representatives and to begin efforts to allow political exiles to return.
In Guatemala, the Government held one brief meeting with leftist rebel representatives, after which the Guatemalan army opened a major offensive in the countryside.
They are now donating tens of thousands of dollars to the rebels, said Hysni Syla, a rebel representative in the United States and Canada.
Neither Mr. Savimbi nor any other rebel representative attended today's meeting, although African diplomats said this week that he was expected to take part.
But the rebel representatives asserted that the Government's demand for a deadline could also complicate the discussions.
But a rebel representative said the encounter had largely been limited to a recital by each side of its respective negotiating position.
A rebel representative stated that the operation was "going easily", with the end target being Gaddafi's Bab al-Azizia compound.
"We are telling them to stop shelling even if they are being shelled," Kabineh Janeh, a rebel representative, said in a telephone interview from Ghana.