Zimbabwe's 87-year-old president Robert Mugabe on Saturday brushed aside calls to step down, telling supporters who endorsed him as candidate in the next presidential election that he would not quit as long as the West maintained sanctions on his party.

Mugabe's allies are pressing for elections next year, instead of 2013 when they are due and when Mugabe would be 89, fearing that he may not cope with the pressure of campaigning.

The veteran leader, who has ruled Zimbabwe since independence from Britain in 1980, said he was lucky to have lived longer than his independence war compatriots and did not plan to retire.

Mugabe was officially endorsed as ZANU-PF presidential candidate for the next election.

Sometimes the call (to retire) comes. It would be wrong, completely wrong when the West is still holding sanctions against us and pursuing regime change, Mugabe said in a speech at the close of the party conference.

It would be an act of cowardice as well. I am not made that way. I am lucky God has given me this longer life than others to be with you. I will not let you down.

A June 2008 U.S. diplomatic cable released by WikiLeaks in September said Mugabe had prostate cancer that had spread to other organs. He was urged by his physician to step down in 2008 but has stayed in the job.

Mugabe has maintained he is still fit.

Mugabe repeated calls for an election next year, saying the coalition government he was forced into with his rival, Prime Minister Morgan Tsvangirai, after disputed elections in 2008 was no longer working.

Mugabe lost to Tsvangirai in the first round of the 2008 presidential vote, which saw his ZANU-PF party losing its parliamentary majority, but went on to win the run-off after a boycott by Tsvangirai citing violence against his supporters.

However, an upbeat Mugabe on Saturday said ZANU-PF was much more vibrant and stronger now than in 2008, pointing to its policies, including a drive to force mining companies to surrender at least 51 percent stakes to blacks as a vote winner.

He said nearly three years of a coalition government with Tsvangirai's Movement for Democratic Change party had exposed his opponents as bereft of ideas.

If we are to go to an election tomorrow, against the chaos of 2008, the disaster, but now with this new vibrancy, surely we'll know how to vote, said Mugabe, who wore a black and yellow shirt emblazoned with his image and white cap.

The inclusive government has frustrated certain decisions, ... that's why we say this inclusive governmental animal must now see its death, he said.

(Reporting by Nelson Banya; Editing by David Cowell)