By Luis Jaime Acosta and Jack Kimball

BOGOTA (Reuters) - Colombian President Juan Manuel Santos will spend two or three days in the hospital after surgery for non-aggressive prostate cancer, his doctor said on Tuesday, a day before the 61-year-old was scheduled for the operation.

Midway through his four-year term, Santos surprised the Andean nation on Monday night when he announced doctors had discovered a cancerous growth, but the disease had been caught in time and there was minimal risk.

Santos is scheduled to have surgery to remove his prostate early on Wednesday after tests showed a malignant tumor, his urologist, Felipe Gomez, told journalists. The cancer will not require chemotherapy, he said.

"The surgery will be performed under regional anesthesia. This means that it is an anesthetic that effects only the lower half of the body, allowing him to retain consciousness," Gomez said outside the Santa Fe hospital in Bogota.

"Following surgery, the patient will be recovering in the same institution and we hope that in the course of two to three days he can return home."

Santos' complete recovery will likely take up to three weeks, according to his doctor. The president is not allowed to travel during that period, but will be able to carry out his official duties.

Gomez said he would give an update on Santos' condition around midday on Wednesday.

The way Colombia's government handled the announcement drew praise from Wall Street. "The situation has been managed well by the government, with absolute transparency," Barclay's Capital said in a note to investors.

Santos, who has three children, joins several other Latin American leaders who have fought cancer in recent years, including Venezuela's Hugo Chavez and Brazilian President Vilma Rousseff.

Chavez has been cagey on the specifics of his cancer, revealing only that it was in his pelvic area.

"I'm sure (Santos) will overcome this disease. I'm sure it will be a successful and good treatment, from my feisty spirit to him, a big hello from all the Venezuelan people," Chavez told reporters in the western state of Yaracuy.

"I wish him good health, recovery and much life."

Government sources said the operation will not affect the start of peace talks with the Revolutionary Armed Forces of Colombia rebels, known as the FARC, which are set to begin in the coming days in Norway and then move to Cuba.

Santos, first as defense minister under his predecessor Alvaro Uribe, then as president, has dealt some of the harshest blows against the FARC guerrillas, including killing the group's leader Alfonso Cano last year.

A successful end to the peace negotiations would secure Santos a place in Colombian history.

(Additional reporting by Eyanir Chinea in Caracas; Editing by Helen Murphy and Todd Eastham)