Looking gaunt and speaking in a scratchy voice, Japanese Prime Minister Shinzo Abe said Monday that ailing health prompted him to suddenly announce his resignation and he apologized to the nation for triggering political confusion.

Abe, 53, announced on Sept. 12 that he wanted to quit — without mentioning his health — and checked into a hospital the following day for stress-related intestinal ailments. He was immediately criticized for not apologizing or fully explaining his decision.

Abe, speaking at a news conference at his Tokyo hospital, said that he didn't think it was appropriate to discuss his health in his original announcement, but that now he regretted that decision.

"After seeing my health deteriorate over the past month, I finally came to the conclusion that I had reached my physical limit," Abe said. "I decided that I did not have the strength to meet my responsibilities as prime minister."

The resignation has thrown the Japanese political world into confusion. The ruling party on Sunday chose moderate Yasuo Fukuda to succeed him, and Fukuda was expected to be elected prime minister in parliament Tuesday.

Abe, who appeared with his doctors, said that he would attend the parliamentary session Tuesday to elect Fukuda as his successor, and that he wanted to continue to serve as a national lawmaker.

"I apologize most of all to the public for the trouble I have caused," Abe said. "Our party faces difficulties in parliament, but I hope to continue in my role as party member ... under the new leadership."

The yearlong government of Abe, whose ratings in public opinion polls had sagged to about 30 percent at the time of his departure, was plagued by scandals and gaffes.

Four of Abe's Cabinet ministers resigned in money-related scandals, including one who quit this month just a week after being appointed. An agriculture minister committed suicide over a scandal in May.

In July, his ruling Liberal Democratic Party suffered a massive electoral setback, losing its majority in parliament's upper house for the first time in decades.

Abe also faced a clash with the main opposition Democratic Party of Japan over extending Japan's mission to refuel coalition warships in the Indian Ocean in support of U.S.-led operations in Afghanistan.

Just days before his resignation, Abe had told leaders at a regional summit that he would stake his job on pushing through an extension.