Japanese Prime Minister Shinzo Abe on Wednesday unveiled a plan to seek a first-ever change to the postwar Constitution, bidding to see the revision take effect in 2020, a specific time frame not publicly mentioned before.

In a video message to a gathering marking the 70th anniversary of the charter's coming into force, Abe, who is also head of the ruling Liberal Democratic Party, proposed making explicit the existence of the Self-Defense Forces in the language of the war-renouncing Constitution, which currently makes no mention of it.

Abe's remarks are likely to draw sharp responses from opposition forces that are against amending the Constitution, especially its Article 9, which stipulates that the Japanese people "forever renounce war" and that "land, sea, and air forces, as well as other war potential, will never be maintained."

"By making explicit the status of the SDF in the Constitution during our generation's lifetime, we should leave no room for contending that (the SDF) may be unconstitutional," Abe said in the video message, delivered to an audience generally supportive of constitutional amendments.

Specifically, Abe proposed referring to the SDF in the Constitution while leaving untouched two paragraphs in Article 9, a change that "deserves popular debate," he said.

The first paragraph of Article 9 says: "Aspiring sincerely to an international peace based on justice and order, the Japanese people forever renounce war as a sovereign right of the nation and the threat or use of force as means of settling international disputes."

It is followed by the paragraph that says: "In order to accomplish the aim of the preceding paragraph, land, sea, and air forces, as well as other war potential, will never be maintained. The right of belligerency of the state will not be recognized."

The government says, however, that the provision does not prohibit the country from maintaining its ability to defend itself, and thus allows Japan to possess defense forces.

A possible revision to Article 9 remains a divisive topic among the Japanese public. A recent Kyodo News survey found that supporters of a change slightly outnumbered opponents, 49 percent to 47 percent, possibly reflecting the depth of concern about North Korea and China's military buildup.

On the overall need to revise the Constitution in the future, 60 percent said it was "necessary" or "somewhat necessary." Supporters of maintaining the current Constitution unchanged totaled 37 percent, according to the mail-in survey.

The current Constitution has never been revised since it went into effect in 1947, nor has a bid been made to initiate a formal amendment process, partly because of the high hurdle in proposing an amendment in parliament before it can be put to a referendum.

A revision to the Constitution, which conservatives often decry as a product of the U.S.-led occupation after Japan's defeat in World War II, has become a more realistic prospect given the LDP's parliamentary majority and the support it has on this issue among lawmakers.

In the video message, Abe said 2020, the year the country is slated to host the Olympics and Paralympics in Tokyo, will be a year in which Japan will "be born anew" and will move forward "in a solid manner."

"I strongly desire that 2020 will be the year a new Constitution goes into force," he added.

"Parliamentarians will soon have to begin concrete discussions in order to present to the people a plan to initiate a constitutional amendment," Abe added.

Among the other issues to be explored as a possible amendment to the Constitution, Abe proposed more debate on making public education free. He said, "As we discuss the future shape of our country, education is an extremely important topic."

Abe, a strong proponent of constitutional amendments who returned as prime minister in December 2012, could serve as LDP president until September 2021 if he wins a third consecutive term as party leader in the next leadership vote in the fall of next year.