Protestors will gather outside Downing Street today as part of an international day of action to demand an end to fighting in Sudan's Darfur region.
More than 10,000 hourglasses filled with fake blood will be overturned by activists across the world in a symbolic gesture to mark the fourth anniversary of the start of the conflict there.
Organisers of the Global Day for Darfur say the demonstrations will illustrate that the "time is up" to help civilians in the troubled region.
The United Nations (UN) estimates that over 200,000 people have died since the start of fighting between the Sudanese government and rebel groups in Darfur, while some two million people have been displaced from their homes as a result of the conflict.
With around four million citizens in Darfur now dependent on aid, celebrities including Sir Elton John and George Clooney have joined campaigners in pressing for action to ease the humanitarian suffering in the Sudanese region.
In a joint statement various artists and musicians accuse the world of having stood by and "watched" the slaughter of thousands of innocent people and warn that the international community "must end its stalling and take decisive action" by securing an immediate ceasefire in Darfur, an end to attacks on civilians and full access to the region for aid agencies.
Speaking ahead of today's planned rally outside No 10, prime minister Tony Blair pledged that Britain would press for "tough action" by the UN security council if the Sudanese government failed to stand by its commitment to restore peace in Darfur.
"The UK and its partners will take tougher action in the security council to target those responsible for the violence, to further restrict access to weapons and to improve monitoring of air flights," Mr Blair warned yesterday.
Sudan's government has accepted a proposal in principal to establish a joint African Union (AU) and UN peacekeeping force in Darfur, but Khartoum has insisted that the AU should assume the leading role in the force, which it wants to be mostly African in composition.
Foreign secretary Margaret Beckett has echoed the words of the prime minister, warning that the Sudanese government has "consistently flouted" security council resolutions and other commitments it has made in the past and stressing that further sanctions will be sought against the administration if the government and rebel movements do not "co-operate fully" with international efforts to secure peace in Darfur.
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