WASHINGTON - President George W. Bush announced further U.S. sanctions against Burma's military rulers on Friday, saying they had continued to defy international demands to "stop their vicious persecution."

Imposing the second package of U.S. measures in less than a month, Bush said he was adding more of Burma's leaders to a list of those already facing financial and travel sanctions and that he had instructed the U.S. Commerce Department to tighten export controls on Burma.

Calling for stepped-up international pressure, Bush also urged China, India and other countries in the region to "review their own laws and policies" with regard to Burma.

"Burma's rulers continue to defy the world's just demands to stop their vicious persecution," Bush told reporters. "They continue to reject the clear will of the Burmese people."

Bush's latest announcement followed weeks of mostly unsuccessful international efforts to get Burma's government to ease up on repression of democracy protesters and open a dialogue with detained opposition leader Aung San Suu Kyi.

Burma's generals have kept a tight lid on the country since soldiers and police crushed Buddhist monk-led street protests that began in late September.

Bush unveiled new sanctions at the U.N. General Assembly last month, toughening U.S. measures that had been in place for years but had forced little change.

Under the latest package, Bush said that "in light of the ongoing atrocities by these men and their associates" he had designated 11 more leaders under existing sanctions and had issued an executive order naming 12 new "individuals and entities" to be covered by U.S. measures.

In announcing further sanctions on Friday, he also appealed to China and India to exert their influence, a tacit admission of the limits of U.S. clout with Burma's rulers.

China is the closest the isolated Burma junta has to an ally, acting as a key trading partner and arms supplier, and is seen as the linchpin for any international pressure campaign. India also has some economic sway with its Asian neighbor.

Bush earlier this week voiced impatience with the international response to the Burma crackdown and threatened further U.S. sanctions.

European Union foreign ministers agreed on Monday to strengthen sanctions against Burma's junta and warned they could go further and ban all new investment.

U.N. envoy Ibrahim Gambari on Thursday praised Beijing for helping to arrange his visit to Yangon earlier this month after the suppression of street protests but said he would press China to lean harder on Burma's junta.

Gambari is due to go to India and then China next week.