TOKYO • Japan is mulling over the use of cruise missiles in response to North Korea's ballistic missile launches and nuclear tests, a move that could invite backlash from proponents of its pacifist Constitution.

The government wants to set aside spending to study the potential acquisition of a means to strike enemy launch sites, possibly in a draft state budget for fiscal 2018, a government official told Kyodo News on Friday.

According to the official, who spoke on condition of anonymity, the long-range American Tomahawk cruise missile, used by the US Navy in land attack operations, is Japan's preferred choice.

Tokyo has stepped up its show of military force amid concerns about a potential nuclear conflict triggered by Pyongyang, sending two naval destroyers to join United States aircraft carrier USS Carl Vinson in exercises off the Korean peninsula. And on Monday, a Japanese warship accompanied a US Navy supply ship headed to join the Carl Vinson and three other warships in a strike group.

Prime Minister Shinzo Abe announced on Wednesday a plan to revise Japan's post-war Constitution that bars the country from maintaining armed forces. He said he wanted to make "explicit the status" of the country's military by amending the Constitution by 2020.

As Japan faces continuing security threats from North Korea, Mr Abe said there should be no room for arguing that the military, with just over 227,000 active-duty troops, "may be unconstitutional".

A panel on security issues in the ruling Liberal Democratic Party is expected to put forward recommendations later this month on how to improve Japan's defence capabilities with an eye on exploring a strike capability option, the Kyodo News reported.

Mr Abe had defended the option to strike at a parliamentary committee meeting on Jan 26, arguing that the deployment is an issue of self-defence should Japan move to attack enemy launch sites when there are no alternatives.