A former rebel leader from Sudan's Darfur region who joined the government says he could leave because of a pro-government assault on a main town.
Mr Minnawi was the only Darfur rebel leader to sign the peace deal
"The situation is critical," said Minni Minnawi, who became a presidential advisor after signing a peace deal.
He says the government is rearming the Arab Janjaweed militia, who he accused of attacking the town of el-Fasher.
At least 200,000 people are estimated to have died and 2m driven from their homes since the conflict began in 2003.
"Even as I am talking to you, we are facing a Janjaweed attack on el-Fasher's cattle market," an angry Mr Minnawi told journalists at his residence in the capital, Khartoum.
He said "only 3% of the peace agreement has been implemented so far", with repeated violations and the destruction of 48 villages in Darfur since the deal was signed in May.
Asked whether members of his Sudan Liberation Movement were putting him under pressure to return to armed rebellion, Mr Minnawi said: "If we have more violations like this and on purpose, we could reach a point when we won't control the decision."
SLM Secretary-General Mustafa Teerab told Reuters news agency that five ex-rebels had been killed in the fighting, along with two civilians.
The Janjaweed have been responsible for many of the worst atrocities in Darfur.
Sudan's army has continued to fight two other rebel groups in Darfur that refused to sign the peace agreement.
Sudan denies supporting the Janjaweed militia, which the United Nations accuses of attacking and killing civilians. But Mr Minnawi last week said it was clear that the government was re-arming the Janjaweed.
Mr Minnawi met Mr Bush in the White House
After signing the peace deal, Mr Minnawi was feted at home and abroad.
He met US President George Bush in Washington, was given an office in the Republican Palace and hundreds of pictures of him were put up on Khartoum's lamp posts.
But the war in Darfur has not stopped and the BBC's Jonah Fisher in Khartoum says every new report of the Janjaweed militia attacking civilians has further eroded Mr Minnawi's credibility.
The Sudanese government is still resisting pressure for the UN to take control of the African Union peacekeeping mission in Darfur.
African leaders have agreed with Sudan that the AU should retain control but that the UN should provide logistical help and the force should be expanded.
But details such as how big the mission will be and exactly what support the UN can provide have still to be agreed.