"If, in the next weeks and next couple of months or so the Sudanese government are not prepared to agree to the UN plan, then we've got to move to sanctions and we've got to move to tougher action," Blair's spokesman quoted the prime minister as saying.
"I think we should certainly consider the option of a no-fly zone to help people in Darfur, because it's a very, very serious situation and it's now spilling into other countries next door."
'Agreed to disagree'
Any no-fly zone would aim to halt the use of Sudanese government aeroplanes and helicopters to support attacks on villages in Darfur.
Sean McCormack, the state department spokesman, said the US president would respond to the idea by considering "what options he thinks are necessary in order to address the grave situation there," saying that the move to consider tougher measures was motivated by a "lack of forward movement on the diplomacy right now combined with an uptick in violence" in Darfur.
However, there were some positive noises from US officials. Andrew Natsios, the US special envoy to Sudan, said he had a productive two-hour meeting with Omar Hassan al-Bashir, Sudan's president, and that next week may still see progress in the country.
|"We agreed to disagree on history"|
US envoy to Sudan
Natsios, who cancelled a trip to Darfur, said: "We agreed to disagree on history, but we have agreed that there are some steps that we can take in the next week that may make some progress."
However he said that the US would only take note of the actions, not the words of the Sudanese government.
Meanwhile the UN Human Rights Council agreed to send a high-level mission to the region to probe allegations of worsening abuses against civilians.
The 47-state council, which is holding its first special session on Darfur, approved a consensus proposal on Wednesday that left the naming of the five "highly qualified" team members up to the council chairman.
Vesa Himanen, Finland's ambassador, said on behalf of the EU following the decision: "I think that we can be proud of this result."
Kofi Annan, the outgoing UN secretary-general, told the opening session on Tuesday that the council must help end the "nightmare" of violence by sending a "clear and united message ... that the current situation is simply unacceptable".
The council, launched in June as part of UN reform, was under pressure to show it can act effectively on Darfur where aid officials say more than 200,000 have died in violence over the past three years.
After two days of haggling over membership of the mission, it was agreed that Luis Alfonso de Alba, the council chairman and Mexican ambassador to the council, should name the team and that it would be accompanied by Sima Samar, the UN special investigator for Sudan.