HARARE, Zimbabwe - Zimbabwe's 87-year-old president said Saturday he would not retire before proposed elections next year and would stay on to lead the country against what he called a Western campaign for regime change.

President Robert Mugabe, addressing 6,000 delegates at the end of his party's annual convention in the second city of Bulawayo, said it would be "an act of cowardice" for him to step down.

"Luckily, God has given me this longer life than others to be with you and I will not let you down," he said.

The four-day convention passed resolutions confirming Mugabe as its sole presidential election candidate and called for polls "early next year without fail."

Speaking in the local Shona language, he said he felt it would be wrong for him to leave now.

The 30-month coalition with the former opposition needed to be "put to death" at elections.

"Let us now start preparing for elections and as we do that we are digging the grave of this monster," he said.

His ZANU-PF party was under siege from Western economic sanctions that tried to dislodge it.

Deep divisions have emerged in Mugabe's party over his ability to remain in control, stop infighting, and contest a rigorous election campaign.

Mugabe has visited Singapore at least eight times this year for medical treatment. U.S. cables quoted on the WikiLeaks Internet site earlier this year cited close associates saying he has prostate cancer.

Speaking for 90 minutes late Saturday, Mugabe said the coalition had failed and opponents blamed the failure on his intransigence and pointed to his age as an obstacle. But, he insisted, some coalition members from Prime Minister Morgan Tsvangirai's party took "a free ride" on the power-sharing deal brokered by regional leaders after disputed and violence-plagued elections in 2008 to benefit from government perks.