Yemen's main opposition group on Saturday accused President Ali Abdullah Saleh of thwarting a Gulf-brokered deal that would see him cede power within a month.

"The authority has thwarted the deal. The Secretary-General of the Gulf Cooperation Council told us that Saleh refused to sign in his role as president. He said he wanted to sign as head of the ruling party, and this is a violation of the text of the Gulf initiative," the official, Sultan al-Atwani, told Reuters.

Saleh, who has ruled the impoverished Arabian Peninsula state for nearly 33 years, was set to sign an agreement on Saturday to quit power in a month's time in exchange for immunity.

Though Saleh in principle accepted the agreement negotiated by the six-state member Gulf Cooperation Council (GCC), the deal was rejected by street protesters demanding his immediate ouster and prosecution.

Saleh, a shrewd political operator considered a key U.S. ally against al Qaeda's Yemen-based wing, had forced mediators to split the signing ceremonies over two days by objecting to the presence of Qatari officials.

Qatar's prime minister was first to state publicly the Gulf deal would seek Saleh's resignation, and its satellite channel Al Jazeera has been blamed by Saleh for inciting revolt in the Arab world, which has been swept by pro-democracy protests.

While the Yemeni leader was due to sign the pact in Sanaa, his party's vice president would travel to the Saudi capital Riyadh for Sunday's official signing ceremony by the opposition, which has warned that further bloodshed could derail the deal.