Tue Sep 25, 7:42 PM ET

UNITED NATIONS - President George W. Bush announced new U.S. sanctions against Myanmar on Tuesday and Western leaders warned the southeast Asian nation's army rulers against crushing pro-democracy protests by force.

Urging all countries to "help the Burmese people reclaim their freedom," Bush told the annual U.N. General Assembly he was imposing financial sanctions and a visa ban on more members of the junta, their supporters and relatives.

His call came before the authorities imposed a dusk-to-dawn curfew and poured security forces into Yangon to try to end the biggest demonstrations against military rule for two decades. Earlier, 10,000 Buddhist monks again defied the generals by marching through the city chanting "democracy, democracy."

"Americans are outraged by the situation in Burma, where a military junta has imposed a 19-year reign of fear," Bush told the world body in his annual speech.

Myanmar was formerly called Burma and its capital Rangoon.

"The United States will tighten economic sanctions on the leaders of the regime and their financial backers," Bush said.

The 27-nation European Union said it would strengthen existing sanctions that include an arms embargo, a travel ban and an assets freeze on junta members "should they resort to using violence against the unarmed and peaceful demonstrators."