( BBC ) - US President George W Bush is to announce new sanctions against the ruling military junta in Burma, the White House has said.
Mr Bush seems poised to impose a US visa ban and financial restrictions on members of the government.
The move comes after eight days of increasingly popular protests against the junta led by Buddhist monks.
The junta, which violently repressed protests in 1988, said it was ready to "take action" against the monks.
Mr Bush is expected to announce the new restrictions during his speech to the United Nations General Assembly.
The BBC's Jonathan Beale, in Washington, says the US has already made clear that it is preparing to take unilateral action against Burma's military dictators.
Washington is also hoping that its steps will encourage other nations to act and embolden the protesters on Burma's streets, he adds.
On Monday Brig Gen Thura Myint Maung, Burma's minister for religion, warned marchers not to break Buddhist "rules and regulations".
He blamed the protests on "destructive elements" opposed to peace in Burma.
The military government has so far showed restraint against the protests.
Monks are highly revered in Burma and correspondents say any move by the junta to crush their demonstrations would spark an outcry.
But there are fears of a repeat of 1988, correspondents say, when the last democracy uprising was crushed by the military and some 3,000 people were killed.
Some monks' representatives had called for the entire country to join them in their campaign to overthrow the government, which began eight days ago.
Monday saw marches in at least 25 towns and cities, including Mandalay, Sittwe and Pakokku.
Turnout estimates in Rangoon, Burma's biggest city, ranged from 50,000 to 100,000.
State television said the demonstrations of the past week were being fomented by communists and exiled media and student groups.
The BBC's Asia correspondent, Andrew Harding, described Monday's marches as a show of defiance unthinkable just a few weeks ago.
Five columns of monks, one reportedly stretching for more than 1km (0.6 miles), entered the city centre to cheers and applause from thousands of bystanders.
Civilians who joined in included officials from the opposition National League for Democracy (NLD) party, led by Aung San Suu Kyi.
The authorities are likely to be under huge pressure from their close neighbour China to avoid bloodshed and instability, our correspondent notes.
The European Union has urged the junta to show the "utmost restraint" in dealing with the protests and to take the opportunity to "launch a process of real political reform".
The exiled Tibetan spiritual leader, the Dalai Lama, has given his backing to the monks' call for freedom and democracy.
UK Ambassador Mark Canning said Burma's leaders were now in uncharted territory but expressed concern about a possible government counter-reaction.
A hard-core group of more than 1,000 of the maroon-robed monks and 400 sympathisers went to Aung San Suu Kyi's street at the end of Monday's march, the Associated Press reported.
They chanted a prayer for peace in the face of the riot police blocking access to her home, where she is under house arrest, before dispersing peacefully.
Monks have been urging Burmese people to hold 15-minute evening prayer vigils.
The organisation that has emerged to lead the protests, the Alliance of All Burmese Buddhist Monks, has vowed to continue marches until it has "wiped the military dictatorship from the land".
The protests were triggered by the government's decision to double the price of fuel last month, hitting people hard in the impoverished nation.