Annan was speaking after meeting with Sudanese President Omar el-Bashir on the sidelines of an Arab League summit in Algeria.
He said he and el-Bashir discussed the conflict in the western Darfur region and "the measures that need to be taken to bring the situation under control and the need for the ceasefire to be respected by both parties...including the rebels."
Annan said a proposal to send peacekeeping forces to Darfur was before the U.N. Security Council and once it is adopted, "it will takes us a couple of months to assemble the troops and get them into the theater."
The council is under mounting international pressure to act quickly but members are still divided over sanctions against the government and punishment for the perpetrators of atrocities.
At the request of the United States, the council voted last week for a second week-long extension of the U.N. political mission in Sudan. But many members including France, Algeria and Britain made clear they are fed up with the delays and want a vote next week on a new resolution.
The U.S.-drafted resolution would establish a broader U.N. mission and authorize a 10,000-strong U.N. peacekeeping force to monitor a peace accord ending the civil war between the government and southern rebels. It would also bolster efforts by the 2,200-strong African Union force in Darfur to promote peace.
Conflict has engulfed Darfur since February 2003, when two non-Arab rebel groups took up arms against the Arab-dominated government to win more political and economic rights for the region's African tribes.
Sudan's Arab government is accused of responding by backing Janjaweed militia that has carried out rapes and killings against Sudanese of African origin. The government denies backing the Janjaweed.
Annan said he also urged the Sudanese government and rebels in southern Sudan to abide by a peace treaty ending Africa's longest-running civil war.
The Navasha peace accord between the Sudanese government and the rebel Sudan People's Liberation Army was signed in Kenya on Jan. 9. The treaty sets out power- and wealth-sharing rules. After six years, the deal says, the south will hold a referendum on whether to remain part of Africa's largest country.