Adding to the pressure on Yemen’s embattled president, several members of his ruling Congress Party resigned Saturday as tens of thousands of people again took to the streets to demand his ouster and Britain warned its citizens against traveling to the impoverished Arab country.

President Ali Abdullah Saleh, a key U.S. ally against an active al-Qaeda offshoot in Yemen, refused to budge, rejecting 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 spread to Yemen at about the time President Hosni Mubarak was stepping down in Egypt in early February. Yemenis, the poorest people in the Arab world, voiced grievances similar to those of the Egyptian protesters — government corruption, poverty and lack of political freedom.

Saleh, who has held on to power for 32 years despite numerous threats to his rule, has failed to quell anti-government sentiment with earlier pledges not to run for reelection in 2013 or install his son as his successor.

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 statement from his office called the opposition’s plan “vague and ambiguous” and said the president reiterated his pledge not to run again when his current term expires in 2013.

Protesters rallied Saturday in Sanaa, the capital, and in Aden, Taiz and Hadramawt. They demanded that the president step down and called for an investigation into the killing of four people during a demonstration Friday in the northern town of Harf Sofyan.

Meanwhile, in response to 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 lawmaker Ali al-Omrani.

Britain’s Foreign Office said Saturday it was advising against all travel to Yemen and warned that the level of consular assistance it could provide in the country was “extremely limited.”

— Associated Press