Negotiations over Darfur may be set to reach a "tipping point", Britain's foreign minister for Africa has warned.
African Union troops are due to leave by the end of the month
Lord Triesman is in New York for talks at the United Nations as it tries to put pressure on Sudanese leaders to help end military action in the area.
He said while the aim was to get Sudan to agree to let UN peacekeepers in to replace African Union (AU) soldiers, no options had been ruled out.
More than 200,000 people have died since a revolt began in 2003.
As many as two million people have been displaced following the violence which has seen the Arab-led Khartoum government in a military campaign against black African groups.
With 12 days until the AU is due to pull out, talks were "key", Lord Triesman said.
He added that anyone who wanted to send troops in without the agreement of the Sudanese government would have to weigh up whether that would end up causing more deaths and displacement.
"I believe we are coming to a key moment in these discussions. I am concerned that we may be arriving at a tipping point."
He added: "As the prime minister has said there are significant disadvantages if the humanitarian crisis is visited on the people of the Sudan and there is not a realistic acceptance of a responsibility to protect their lives."
He said the full deployment of UN troops could take up to three months and urged the AU to stay on for that long.
Sudanese President Omar al-Bashir was also in New York under growing pressure to allow UN peacekeepers into Darfur if AU troops do not stay on.
Earlier, Foreign Secretary Margaret Beckett said it would be counterproductive to try to send in UN troops without Sudan's acceptance.
On Saturday, UK Prime Minister Tony Blair wrote to leaders of the European Union, calling the situation in Darfur "unacceptable" and urging them to take a common stand on the issue.