Sudanese Government and rebel leaders have committed to signing a peace deal to end the country's civil war by the end of the year, US Secretary of State Colin Powell has said.
The US is putting pressure on both sides to end the war
After meeting representatives of both sides, Mr Powell said they would be invited to the White House by US President George W Bush for a signing ceremony once a comprehensive agreement is completed.
The BBC's Alastair Leithead in Kenya, where the Sudan talks have been taking place, says it is the first time the sides have committed themselves to a timescale for ending the conflict.
The 20 years of fighting pitting rebels from the Christian and animist south against the Islamic government has left more than 1.5 million people dead.
Sudan's Vice President Ali Osman Taha and southern rebel leader John Garang both said they were determined to reach a peace settlement at the talks, in the Kenyan lakeside town of Naivasha.
But they pointed to the difficulties which still lay ahead.
"The issues are not easy, but with determination and commitment, we can overcome," Mr Taha said.
"We have surmounted one hill and there are a series of hills to surmount hopefully by December," said the rebel leader.
The BBC's Alfred Taban in the Sudanese capital, Khartoum, says people's hopes have been raised that peace can come and US sanctions on Sudan can be lifted.
However, he says that Islamist groups are unhappy with the US involvement in the Sudanese peace process, accusing the Americans of backing the southern rebels.
"I can see the end is in sight," Mr Powell said.
Whether Islamic law will apply in the capital, Khartoum
How oil revenue is shared out
What type of international supervision will take place
The status of three central areas: Abyei; Blue Nile State and Nuba Mountains
"This is a moment of opportunity that must not be lost... the way is now open for a final and comprehensive solution."
Mr Powell said it was essential to move forward to an agreement to end the suffering of the Sudanese people.
He said leaders on both sides had to complete "the final stage of this marathon" so that Sudan could "experience a new way of life unclouded by the suffering of war."
Previous talks ended last month with an agreement on security during a six-year transition period, before a referendum on the future of the south.
The key remaining issues to be discussed include the distribution of Sudan's oil wealth and how power will be shared in the capital.
The week-long talks will also discuss what will happen to three contentious areas - Abyei, Blue Nile State and the Nuba mountains - that fall between northern and southern Sudan.
The US has listed Sudan as a "state sponsor of terrorism", claiming Palestinian militant groups such as Hamas and Islamic Jihad are operating from Khartoum.
Nonetheless it has long held an interest in the future of the country, with Mr Powell referring to its plight in remarks to Congress after he was sworn in as US secretary of state three years ago.
Sudan has been torn apart by 20 years of fighting
BBC Africa reporter Martin Plaut says US concerns over fighting terrorism, ensuring access to Sudanese oil and supporting the country's Christian south all play a part in Washington's interest in the peace process.
Regional observers say without US pressure, the Sudanese peace talks would never even have begun.
They say the US also has the power to either aid or severely hinder both sides should negotiations fail.