YANGON, Myanmar - Myanmar's military regime yesterday extended the house arrest of democracy activist Aung San Suu Kyi, refusing to bow to international pressure of the sort that persuaded the generals to let in foreign help for cyclone victims.

The detention of Suu Kyi, a Nobel peace laureate who has been detained for more than 12 of the last 18 years, has been extended for one year, said a government official who spoke on condition of anonymity because he was not authorized to speak to the media.

Her detention has long been the symbol of the regime's heavy-handed intolerance of democratic opposition to its rule. A worldwide campaign is lobbying for her release.

President Bush said that he was "deeply troubled" by the extension of Suu Kyi's house arrest but that the United States would continue to provide aid for Myanmar's cyclone survivors.

The extension of Suu Kyi's detention came as Myanmar was still fending off worldwide criticism for its inadequate aid effort after Cyclone Nargis. The storm left an estimated 2.4 million people in desperate need of food, shelter and medical care, according to the United Nations. The government says the deluge killed 78,000 people and left 56,000 missing.

Only after intense international pressure and a personal appeal by U.N. Secretary-General Ban Ki-moon, who flew to Myanmar last week for talks with the junta's chief, Senior Gen. Than Shwe, did the government relent and agree to let foreign relief workers into the Irrawaddy River delta, the area hit hardest by the cyclone.

"International aid workers are starting to move to the delta," said Richard Horsey, a spokesman for the U.N. humanitarian effort. Helicopters also began shuttling high-energy biscuits and ready-to-eat meals into the hardest-hit area yesterday, he said in Bangkok, Thailand.

Myanmar's leaders are leery of foreign aid workers and international agencies because they fear an influx of outsiders could undermine their control. The junta is also hesitant to have its people see aid coming directly from countries such as the United States, which it treats as a hostile power seeking to invade or colonize.

But Suu Kyi, daughter of the country's martyred independence leader, Gen. Aung San, has long been regarded by the generals as the biggest threat to their power. Her National League for Democracy party is the country's largest legal opposition group, and it retains the loyalty of millions of citizens despite two decades of government repression.

The party won the most seats in 1990 elections, but the military refused to convene parliament. Instead, it harassed and arrested members of the party, setting a pattern that still stands.

Suu Kyi's latest period of detention started in May 2003 after a motorcade in which she was traveling was attacked by a pro-government mob. An unknown number of her followers were killed in the attack, which was regarded by some diplomats as an assassination attempt.

She has appeared in public only once in the last five years; she was allowed to stand at the open gate of her compound during September's pro-democracy protests in Yangon. Only a few hundred demonstrators who were allowed to march down her street got a glimpse of her.

She was awarded the Nobel Peace Prize in absentia in 1991 for her nonviolent attempts at promoting democracy.