"The European Union is ready to help finance this operation. It could finance more than half the cost of the operation - over 100 million euros ($126 million) could be given together with technical support, expertise and planning," the diplomat said on Friday.
The AU's Peace and Security Council agreed on Wednesday to expand its presence in Darfur, deploying an enlarged and more robust peacekeeping force of about 3000 mainly Rwandan troops.
The diplomat said deployment was likely to start next week.
"Solana's trip has been tailored to the context of launching a major African Union operation," the diplomat said. "The substantial EU contribution is in the process of being agreed."
Thousands have starved to death
in recent months, the UN says
The crisis in Darfur in western Sudan erupted after years of
skirmishes between nomads and farmers over scarce resources in the arid region. Rebels took up arms early last year, accusing the government of neglecting Darfur.
Rebels say the government has used militias known as Janjawid to put down their rebellion and to loot and burn villages. The Sudanese government admits arming some militias to fight the rebels but denies links to the Janjawid, calling them outlaws.
The United Nations estimates 70,000 people have died from malnutrition and disease in the past seven months alone, although the Sudanese government disputes this.
The EU diplomat said Canada, the United States and Australia had agreed to contribute to the peacekeeping operation, mainly by providing transport to get the 3000 troops and all the food and equipment they would need to remote parts of Darfur.
Solana will start his trip in Ethiopia, where he arrives on Friday evening and will hold talks with AU Commission President Alpha Oumar Konare and other officials on Saturday, his spokeswoman Cristina Gallach said.
He will also hold talks with Ethiopian Prime Minister Meles Zenawi before travelling to Khartoum on Saturday. In Sudan, Solana is expected to meet President Umar Hasan al-Bashir and other senior officials before returning to Brussels on Sunday .