President Ali Abdullah Saleh, a U.S. ally in the War on Terror, said Saturday he would run for another term in September because of "the people's pressure" to reverse his earlier decision to step down.

Saleh, who has ruled since 1978, said in July 2005 he would not seek another seven-year mandate because he wanted to open the way for the peaceful transfer of power.

Saturday's announcement was the second time Saleh changed his mind about a promise not to run, having done so in 1999 — the first time he faced a direct vote.

"I comply with the people's pressure and upon the people's desire, I will in run the coming polls," Saleh told tens of thousands of cheering supporters.

Yemen, the ancestral homeland of Al Qaeda leader Usama bin Laden, had long been a haven for Islamists and was the scene of the October 2000 suicide bombing of the USS Cole that killed 17 American sailors.

But after the Sept. 11 attacks, Yemen allied with the United States in the War on Terror and waged a crackdown on militants.

The United States has since provided equipment to Yemen's military to beef up port and border controls and trained Yemeni security forces to battle militants.

On Saturday, students, civil servants and tribal leaders gathered outside the stadium where Saleh's General Congress Party was holding a convention to nominate its candidate for the polls. They waved signs and banners reading "Continue the path," "We accept nobody but you" and "We'd sacrifice our blood and souls for you, Ali."

Saleh's party had pressed him since the convention opened Thursday to join the race.

Earlier in his speech Saturday, Saleh mentioned what he said were "the chants, statements, messages, poems and calls by scholars, intellectuals, civil society and political parties" urging him to run.

An opposition figure said that the announcement was expected.

"We knew that the president would reach this result ... It is a farce. He is a comedian," Mohammed al-Mugaleh of the Socialist Party told The Associated Press on Saturday.

Opposition figures were skeptical about Saleh's announcement last year, viewing it as a ploy to provoke popular calls for him to run again or to open the way for his son, Ahmed, 39, to take the top job.

The opposition agreed Friday to name a single candidate to run against Saleh. They have not announced their choice.

On Saturday, thousands of security forces were deployed around the country and the capital, and authorities arrested 15 political activists in a bid to prevent demonstrations urging Saleh not to run.

But in the province of Umran north of San'a, some 5,000 demonstrators from the al-Hasheed tribe, one of the country's largest, urged Saleh to stick to his earlier decision to not run.

Saleh ruled first as president of North Yemen and then as head of the unified state after the May 1990 merger of North and South.

The shrewd politician has remained in power by keeping a lock on the military, forming alliances among the country's often fractious tribes and allying himself with Islamists — particularly during Yemen's 1994 civil war against socialists in the south.

Saleh has been able to avoid confrontation with political Islamic groups despite the crackdown and to avoid serious challenge despite the ailing economy.

He is credited with paving the way for Yemen's discovery of oil in 1986, but the government has been accused of rampant corruption and failing to pump oil wealth into the economy. Unemployment currently runs at 36 percent.

Last July, eight people were killed in riots after the government announced it would lift subsidies on oil products.