TOKYO (Reuters) -- A majority of Japanese favor letting women inherit the imperial throne but slightly more than half are opposed to a quick revision of the males-only succession law, a survey showed on Sunday, after news that a princess is pregnant with a possible male heir.

The survey was published in the Mainichi newspaper after a surprise announcement last week that Princess Kiko, wife of Emperor Akihito's second son, is pregnant with her third child, raising hopes that a male heir might be born for the first time in four decades.

News of Kiko's pregnancy prompted Prime Minister Junichiro Koizumi to back away from his pledge to submit a bill revising the imperial succession law to the current session of parliament.

"We must debate and study the issue in a quiet atmosphere," ruling Liberal Democratic Party (LDP) Secretary General Tsutomu Takebe told public broadcaster NHK on Sunday. "What is important is the agreement of the people," Takebe added. "It is true that Princess Kiko's pregnancy has changed things greatly."

A 1947 law limits succession to males descended from an emperor through the paternal line.

No males have been born into Japan's ancient royal family since the birth of Kiko's husband, Prince Akishino, in 1965.

Fifty-five percent of those responding to the Mainichi survey on Friday and Saturday said they opposed revising the succession law in the current session of parliament which ends in June, while 39 percent were in favour.

As many as 78 percent said they supported the notion of a female emperor, while 65 percent also favoured letting a reigning empress's child inherit the throne.

Fifty-two percent said changing the imperial succession law would be necessary even if Kiko bears a son.

Advisers to the prime minister urged last November that the law be revised to let women and their children inherit the throne to avoid a succession crisis. ------------- Second best

Conservatives opposed to the revisions had been mounting a campaign to block submission of the bill to parliament even before news of Kiko's pregnancy.

Traditionalists -- many of them in the LDP -- want to maintain a male line they say stretches back more than 2,000 years, and some have suggested reviving princely houses abolished after World War Two, or even bringing back royal concubinage.

Japan has had eight reigning empresses, the last in the 18th century, but conservatives stress that none passed the throne on to a child who was not of the imperial paternal line.

Several mainstream Japanese newspapers have come out in support of waiting until Princess Kiko's child is born, but the English language Japan Times criticised those favouring delay.

"The readiness of many people to see the new plan shelved or postponed suggests that the idea of equality has only shallow roots here: a woman is still second-best, a last resort," the newspaper said in an editorial on Sunday.

Crown Prince Naruhito, 45, and Crown Princess Masako, 42, have one child, the 4-year-old Princess Aiko, who would become second in line to the throne if the succession law is revised.

Under the current law, if Princess Kiko bears a son, he would be third in line after his father, Akishino.

Proponents of revising the law have argued that changes should be enacted soon, since the education of a heir to a position devoid of political power but steeped in symbolism usually begins around the age of three.