Increasing pressure on Yemen's embattled president, several members of his ruling Congress Party resigned Saturday as tens of thousands again took to the streets to demand his ouster and Britain warned its citizens against all travel to the impoverished Arab nation.
President Ali Abdullah Saleh, a key U.S. ally in fighting a potent al-Qaida offshoot in his country, was refusing to budge and rejected a proposal from a coalition of opposition groups to end the political standoff by agreeing to step down by year's end.
The region-wide unrest hit Yemen just around the time President Hosni Mubarak was stepping down in Egypt in early February. Yemenis, the poorest people in the Arab world, had similar complaints over government corruption, poverty and a lack of political freedom.
Saleh, who has held on to power for 32 years despite numerous threats to his rule, has failed to quell the anti-government outpouring with a pledge not to run for re-election in 2013. He also promised not to install his son as a successor, as many suspected he was intent to do.
Nevertheless, in a sign that he still feels he has room to maneuver, Saleh on Saturday rejected his opponents' suggestion that he quit sooner.
A press statement from the president's office said the opposition's "five-point plan is vague and ambiguous" and that the president reiterated his pledge not to run again when his current term expires in 2013.
"The constitution is a reference for all (of us) and any attempt to violate it cannot be accepted," the statement said.
Saleh's reference to the constitution drew scoffs from protesters.
"The regime's adherence to the rules of the constitution is pathetic because this regime itself has trampled on the constitution over long decades," said Redwan Massoud, a protest leader at the capital's Sanaa University.
Massoud said protesters were not interested in dialogue.
"Our only demand is that the president should leave," he said.
The government has suspended classes at universities in the capital, Sanaa, and the southern port city of Aden that have been focal points for daily demonstrations inspired by the uprisings in Egypt and Tunisia.
Protesters rallied Saturday in the main squares of Sanaa, Aden, Taiz and Hadramawt. They demanded the president step down and called for an investigation into the killing of four people during Friday's protest in the northern town of Harf Sofyan.
Meanwhile, protesting Saleh's handling of the increasingly tense standoff, several members of his ruling party resigned, including Saleh Samei, the former minister of expatriate affairs, and parliament member Ali al-Omrani.
Britain's Foreign Office said Saturday it was now advising against all travel to Yemen and warned that the level of consular assistance it could provide in the country was "extremely limited."
The opposition's proposal doesn't detail how Saleh would hand over power. Opposition spokesman Mohammed al-Sabri said the expectation is that the president would come forward with his own proposal to transition from power.
Saleh has called for a unity government to be formed with the opposition, an idea that has repeatedly been rejected.
Saleh has been an important U.S. ally in the fight against al-Qaida, receiving tens of millions of dollars in U.S. military and other aid and quietly allowing American drone strikes on al-Qaida targets.