US President George W Bush has announced further sanctions against Burma's ruling junta.
Monks are still being arrested, according to a senior UK diplomat
Mr Bush ordered a tightening of export controls, and urged India and China - who have extensive trade ties with Burma - to apply more pressure.
And he asked the Treasury Department to freeze the financial assets of members of the military regime not covered by previous measures.
The announcement follows the violent suppression of anti-government protest.
The country's leaders had continued to defy international demands to "stop their vicious persecution", Mr Bush said.
The US has already imposed substantial trade, investment and diplomatic sanctions on the regime, freezing assets and imposing visa bans on senior generals and their families.
"Monks have been beaten and killed. Thousands of pro-democracy protesters have been arrested," said Mr Bush in a White House statement on Friday.
"Burma's rulers continue to defy the world's just demand to stop their vicious persecution."
"We are confident that the day is coming when freedom's tide will reach the shores of Burma."
Just days ago, the European Union stepped up its sanctions against the regime.
Japan, one of Burma's biggest aid donors, has also cut more than $4m (£1.95m) in funds.
CLAMPING DOWN ON BURMA
Military leaders' US assets frozen
US visa ban imposed on top generals and their families
US citizens banned from dealing with junta leaders
EU import embargo on timber, gems and precious metals
$4m of Japanese aid cut
But it is not clear what impact such economic measures will have, with critics arguing sanctions are largely ineffective.
Washington's Cato Institute estimates that unilateral sanctions imposed by the US between 1970 and 1998 failed almost 90% of the time.
China, India and Russia have all called for a more conciliatory approach towards Burma's junta, limiting the impact of any sanctions imposed.
And as China is a veto-holding member of the Security Council, it has the power to block any potential UN motion about sanctions.
It is also argued that sanctions hit the civilian population hardest while hardening the regime's resolve against democratic reform.
2,500 still held
A senior British diplomat has told the BBC that some 2,500 people are still being held by the military.
British officials have also received first-hand accounts of the grim conditions under which many detainees are being held.
UN envoy Ibrahim Gambari will visit Burma next month
Eyewitness accounts speak of detainees being held in excrement-smeared rooms suffering beatings and interrogations.
Uncertainty also still surrounds the fate of thousands of Buddhist monks, many of whom have been bottled up in the larger monasteries or dispersed to the countryside.
While the government is seeking to present the recent disturbances as "local difficulty that has since been contained", the diplomat said things were still very far from normal.
Describing Burma as "in many respects a nation of prisons", he said serious human rights abuses were continuing.
He said there were still regular night-time raids by the police or the military, scooping up hundreds of people.
The senior British diplomat noted that there was a profound sense of trauma among the wider Burmese population.
It was hard, he said, for outsiders to understand the scale of the insult that had been delivered to the monks which had created huge underlying pressures in the country despite the security crackdown.