Yemen's opposition rejected an offer on Thursday to join Gulf-mediated talks in Saudi Arabia on a transfer of power and set a two-week deadline for President Ali Abdullah Saleh to step aside.
Gulf Arab foreign ministers had said they would invite Saleh, who has faced two months of street protests demanding his resignation, and his opponents to mediation talks on a transfer of power. However, the opposition has seesawed on the offer.
"We have renewed our emphasis on the need for speeding the process of (Saleh) standing down to within two weeks. Therefore we will not go to Riyadh," said Mohammed al-Mutawakkil, a prominent opposition leader.
Saudi and Western allies of Yemen fear a prolonged standoff in the Arabian Peninsula state could ignite clashes between rival military units in the capital and elsewhere and cause chaos which would benefit an active Yemen-based al Qaeda wing.
Yemen's opposition first rejected a Gulf Cooperation Council statement on the framework for the talks, which had been due to take place in Riyadh, because it appeared to offer Saleh a waiver from future prosecution and did not call for an immediate handover.
Later, they met the ambassadors of Saudi Arabia, Oman and Kuwait on Tuesday seeking clarification of the GCC understanding of a "transfer of power", which does not specify a time frame for Saleh to step down.
Some opposition leaders had hinted that talks could start as early as Saturday, before Mutawakkil said the clarifications offered by Gulf ambassadors had been inadequate.
"We didn't find in the clarifications that the ambassadors presented anything that meets our demands for an immediate removal," Mutawakkil said.
"There was nothing new from the Gulf Cooperation Council ambassadors."
Saleh has accepted the talks framework, while another key player, General Ali Mohsen, a kinsman of Saleh's whose units are protecting protesters in Sanaa, has welcomed the GCC plan.
A transfer of power in Yemen could technically last until the next presidential election scheduled for 2013, a prospect the opposition finds unacceptable.
Saleh has offered new parliamentary and presidential elections this year as part of political reforms, but says he should stay in power to oversee the change or hand over to what he calls "safe hands".