Carter is one of four "Elders" meeting with government officials in Khartoum and regional leaders in the western region that has been wracked by violence for four years.
Carter told the BBC Bashir had pledged $100 million to the effort, while another $200 million was a loan from China.
He said Bashir had also agreed to allow international observers to monitor elections scheduled for 2009.
Carter is part of the Elders delegation founded by former South African President Nelson Mandela as a peacemaking diplomatic group. The other members are South African Archbishop Desmond Tutu, U.N. envoy Lakhar Brahimi and rights activist Graca Machel.
Some 200,000 people have been killed in the tribal fighting that has displaced more than 2 million people.
A 7,000-member African Union peacekeeping force will be joined by a 26,000-member U.N. force by the end of the year.