Japan's ruling Liberal Democratic Party is set to begin internal discussions on nuclear deterrence, taking up the controversial issue of nuclear sharing with the United States, party lawmakers said Monday despite the government's stance against the option.

Russia's invasion of Ukraine and its threat of using nuclear weapons have prompted calls from conservative members including former Prime Minister Shinzo Abe for Japan to discuss the topic.

Former Japanese Prime Minister Shinzo Abe. (Kyodo)

The LDP's panel on national security will hear expert opinions on U.S. and European nuclear deterrence strategies on Wednesday and exchange views, the party sources said.

Japan, which suffered the U.S. atomic bombings of Hiroshima and Nagasaki in World War II, upholds the three principles of not possessing, not producing and not allowing nuclear weapons on its soil. For years, it has relied on the U.S. nuclear umbrella for deterrence.

Designed to provide collective security for its members, the North Atlantic Treaty Organization has nuclear sharing arrangements, under which non-nuclear states host U.S. nuclear weapons for use in the event of a war.

A few days after Russia invaded Ukraine in late February, Abe said Japan should start discussing whether to seek a nuclear sharing arrangement similar to NATO's, without a "taboo."

Sanae Takaichi, the LDP's policy chief who shares a hawkish stance on security with Abe, has said in the event of a contingency there should be an exception to one of the three nuclear principles of "not allowing" nuclear weapons to be brought to Japan.

Prime Minister Fumio Kishida has dismissed the possibility that the government will start its own discussions about a potential nuclear sharing arrangement.

Japanese Prime Minister Fumio Kishida speaks during a House of Councillors budget committee session in Tokyo on March 14, 2022. (Kyodo) ==Kyodo

"Under the Japan-U.S. alliance, extended deterrence is working," Kishida told a parliamentary session on Monday, referring to the state of Japan's security being ensured under the U.S. nuclear umbrella and by its military forces.

"The government is not planning to start discussions about nuclear sharing," Kishida told the parliamentary session.

The latest push by conservative members of the LDP comes as Kishida, elected from a constituency in Hiroshima, has been pushing for a world free of nuclear weapons.

This year, Japan is planning to review its national security strategy adopted in 2013 when Abe was prime minister and two other key documents on defense policy and equipment, to reflect the security environment around Japan that Kishida has said has been getting "severer rapidly."

Japan neighbors both nuclear state China and North Korea, whose nuclear and missile development remains a security concern. It also has a territorial dispute with another nuclear power Russia.

Related coverage:

Ex-Japan PM Abe wants attempts to alter status quo in Asia quashed

Kishida says Japan won't seek nuclear sharing with U.S.

Ex-PM Abe says Japan should discuss nuclear sharing arrangement