HARARE, Zimbabwe — Robert Mugabe, 93, who ruled Zimbabwe with an iron grip until the military placed him under house arrest last week, shocked the nation on Sunday night by refusing to say whether he would resign.

Many political observers and fellow Zimbabweans had been expecting Mr. Mugabe to step down as president after nearly 40 years in power. But the embattled president gave a 20-minute televised speech that acknowledged problems in the nation — and he vowed to soldier on.

“The era of victimization and arbitrary decisions” must end, Mr. Mugabe said while sitting at a table, flanked by members of the military and other officials, including a priest.

He also declared that he would oversee his governing party’s congress in a few weeks. “I will preside over its processes, which must not be prepossessed by any acts calculated to undermine it or to compromise the outcomes in the eyes of the public,” he said.