"I hope we can move forward to realize the necessary agreement to find a solution to this conflict," Mr Santos said in a televised address.

All sides in Colombia want an end to more than 50 years of fighting.

However opponents of the government insist on a renegotiation of part of the peace deal.

Led by the former President, Alvaro Uribe, they say they do not want the rebels to be guaranteed seats in Congress, or their leaders offered immunity from prison.

President Santos is due to meet with Uribe and Andres Pastrana, another former president.

The peace agreement was reached after four years of formal talks in the Cuban capital, Havana, between government and Farc negotiators.

From early on in the negotiations, President Santos announced he would put the final agreement to the Colombian people in a "yes" or "no" vote.

Polls suggested the agreement would be approved by a comfortable margin, but the deal was rejected by 50.2% of voters.

Both President Santos, who won a second term in office in 2014 on a promise of reaching a peace deal, and Farc leader Timochenko have insisted they will not give up.

In a video message from Cuba, Timochenko said "peace had come to stay".

He said the rebels would continue to observe the bilateral ceasefire they had signed with the government and abide by what they had agreed with the Colombian government.

"The warmongering of those who want to sabotage this peace with dignity will never be stronger than the feelings of harmony, inclusion and social justice," he added.

Earlier he had said that the rebels were prepared to "fix" the deal and that the result of Sunday's vote "does not mean the battle for peace is lost".