Odinga, one of Mugabe's most outspoken critics among African leaders, said the deal signed between Mugabe and opposition leader Morgan Tsvangirai on Monday opened "a window of hope".

Speaking in London, he said Tsvangirai's Movement for Democratic Change (MDC) should enter negotiations knowing it has the upper hand, given it had won a first round of elections, which he said was the only poll accepted internationally.

"Therefore Mr Mugabe is not president, therefore they should not negotiate with Mr Mugabe from a position of weakness," Odinga said at an event at the Houses of Parliament, hosted by the London-based think-tank, the Royal Institute of International Affairs.

"Then be flexible enough to reach a compromise which will give Mr Mugabe a place to exit... For the sake of the people in Zimbabwe, we must give Mr Mugabe a safe exit," he added.

Both Mugabe and Tsvangirai have demanded to be recognised as Zimbabwe's rightful president. Tsvangirai refused to take part in the run-off election, citing attacks on his supporters. Mugabe was declared the victor.

Despite the recent crisis in Kenya, Odinga stressed the differences between Zimbabwe and his country -- in political, economic and military terms.

Kenya's own presidential election, in December 2007, was disputed and led to two months of violence in which about 1,500 people were killed and more than 300,000 made homeless. Peace was restored with the formation of a coalition government between President Mwai Kibaki and Odinga's former opposition party.

Odinga said Kenya did not provide a blueprint for the way forward in Zimbabwe "except on the need to open dialogue."

Odinga, who is also attending an investment conference in London, said his country was back on its feet after the period of violence and urged investors and tourists to return.

"We have been to hell and back and never again in our history will we return to those times," he said. "Our nation is back on its feet. Kenya is up and kicking."