NAIROBI, Kenya — Kenya's political rivals agreed Thursday to write a new constitution within a year as part of a deal to end postelection violence which has already killed more than 1,000 people, a government negotiator said.

In Washington, President Bush said he will dispatch Secretary of State Condoleezza Rice to Kenya to demand an immediate halt to violence that broke out after the disputed Dec. 27 presidential election.

Former U.N. chief Kofi Annan, who is mediating in the Kenya crisis, has hammered out a deal between the rival camps, a spokesman said earlier Thursday. But the full details have not yet been released.

"The two parties agreed to write a new constitution," government negotiator Mutula Kilonzo told The Associated Press after two days of secret talks were adjourned until Monday.