The Japanese government has been working on plans to respond to a potential crisis on the Korean Peninsula since February in light of increased pressure on North Korea from the United States, government sources said Thursday.

Discussions in the National Security Council have so far included a plan to evacuate Japanese nationals from South Korea and measures to respond to the risk of North Korean soldiers trying to enter Japan disguised as refugees, the sources said.

The plans come in response to the administration of U.S. President Donald Trump saying all options, including military action, are "on the table" in tackling Pyongyang's nuclear weapon and ballistic missile development efforts -- a departure from the "strategic patience" doctrine of Trump's predecessor Barack Obama.

Tokyo apparently judged it urgently needs to update its policy on emergency responses to crises, drawn up in 1996 alongside a revision of the Japan-U.S. defense cooperation guidelines.

At the same time, the administration of Prime Minister Shinzo Abe is aiming to appeal to all sides of the North Korea situation through its doctrine of "dialogue and pressure," including by urging China to use its influence on the country.

According to the sources, Abe called an NSC ministerial meeting on Feb. 23 after his summit with Trump in the United States earlier that month.

Abe instructed Deputy Chief Cabinet Secretary Kazuhiro Sugita and others to come up with crisis plans, having judged that increased U.S. pressure on North Korea could raise the possibility of unrest, the sources said.

The attendees at that meeting forecast that a crisis on the peninsula could result in a great number of refugees turning up in boats along Japan's Sea of Japan coast.

They called for preparations for a humanitarian response, as well as enhanced security in light of the possibility that North Korean soldiers could enter Japan pretending to be refugees, the sources said.

In order to safely evacuate the 60,000 Japanese nationals, including tourists, estimated to be in South Korea at any given time, the attendees looked at asking the U.S. military in South Korea to help ensure their safety or sending aircraft or ships from the Self-Defense Forces to pick them up with Seoul's approval.

The ministerial meeting brought together Deputy Prime Minister Taro Aso, Chief Cabinet Secretary Yoshihide Suga, Foreign Minister Fumio Kishida and Defense Minister Tomomi Inada.