More than a million people in Sudan have fled their homes

But the prime minister said there was a "moral responsibility" to deal with the situation "by any means we can".

UN Secretary General Kofi Annan has said Sudan is not protecting people in the Darfur region, where widespread atrocities have been alleged.

Foreign Secretary Jack Straw plans to visit the crisis-hit country.

Thousands killed

Mr Straw will travel to the region next month as efforts continue to agree a UN Security Council resolution urging the Sudanese government to curb the conflict.

He is also pressing the EU to fund the Africa Union (AU) monitoring mission in the country, supervising a ceasefire between official government forces and rebel armies.

I believe we have a moral responsibility to deal with this and deal with it by any means we can Tony Blair

The mission could include British personnel with military expertise, but Mr Straw stressed it would not be a fighting force.

More than a million people have been driven from their homes around Darfur as government-backed Janjawid militias hit back at rebel attacks on the administration.

'Complicit'

The refugees are being helped by international aid agencies and donations from abroad, including more than �63m from the UK.

Mr Straw said: "The Sudan army is at best passive and at worst complicit in these attacks.

"For the peacekeeping to be effective the Sudanese government has to stop the fighting. That's why we are sending very strong messages to the Sudanese."

Earlier, at his monthly press conference, Mr Blair said reports he had asked Downing Street and Foreign Office officials to draw up plans for possible military intervention in Sudan were "premature," but nothing had been ruled out.

The "critical thing," in the short-term, was to try and make the current international strategy work, adding "we want the European Union to make a far bigger commitment on this," he told reporters.

"I believe we have a moral responsibility to deal with this and deal with it by any means we can," he added.

Massacre denied

Conservative Shadow international development spokesman John Bercow said there was "a good case" for considering military action in Sudan.

"Foreign policy has not been robust enough," Mr Bercow told BBC Radio 4's World at One.

The Janjaweed - an Arab militia - are accused of carrying out a campaign of terror in the Darfure region and using mass rape against villagers.

Earlier this month the Sudanese government agreed to disarm the Janjaweed and other armed groups.

It also said it would take steps to protect those displaced.

In an interview with the BBC, Sudanese Interior Minister Abdulrahim Mohammed Hussein denied there had been massacres in Darfur.

"Disarming the militias is a long process that required patience," he said.

"Implementation of these commitments has been so far uneven," Mr Annan said.

US 'Dissatisfied'

He is due to meet US Secretary of State Colin Powell on Thursday to discuss the Darfur crisis.

"It's time to get together now to look very carefully at the situation," State Department spokesman Richard Boucher said.

On Tuesday Mr Powell has said the international community was "completely dissatisfied" with Sudan.

"Not enough is being done to break the hold of the Janjaweed," he said on Tuesday. "Rapes are still occurring."

The conflict in the region started last year, after a rebel group began attacking government targets saying the region was being neglected by Khartoum.

The rebels say the government is oppressing black Africans in favour of Arabs.