SEOUL - South Korea and the United States have reaffirmed their solid defence partnership, agreeing that a "strong, effective and credible" military response can underscore diplomatic efforts to resolve the North Korea nuclear issue.

US Defence Secretary James Mattis, in talks with South Korea's Defence Minister Song Young Moo in Washington on Wednesday (Aug 30), assured his counterpart that the US remains committed to defending its ally from any North Korean attack with an "effective and overwhelming response".

The two also jointly condemned North Korea's "reckless, provocative and destructive" behaviour, including the launch of two intercontinental range missiles last month (July), and the latest intermediate-range missile that flew over Japan on Tuesday.

"The two ministers expressed their support for the ongoing diplomatic efforts to denuclearise the Korean Peninsula, while emphasising the need to have a strong, effective and credible military response to enhance the credibility of the diplomatic efforts," South Korea's Defence Ministry said in a press statement.

This marks Mr Song's first meeting with Mr Mattis since taking office last month (July), as part of regular bilateral visits. He is also scheduled to meet US Pacific Command chief, Admiral Harry Harris, in Hawaii before returning to Seoul on Friday (Sep 1).

In Washington, Mr Song and Mr Mattis agreed to further discuss how to revise 2012 bilateral missile guidelines to improve their joint response to North Korea's growing nuclear and missile threats, and to accelerate efforts to transfer wartime operational control from Washington to Seoul.

South Korea will also boost its own military systems to counter the North, including the Kill Chain preemptive strike system and the Korean Air and Missile Defence system.

Mr Song, a former navy chief, told reporters after the meeting that he and Mr Mattis "saw eye to eye" on the need to increase the payload for missiles. Seoul had reportedly requested to double the payload from 500kg to one tonne.

He also raised the issue of redeploying US tactical nuclear weapons to the Korean Peninsula and Seoul's consideration of building nuclear-powered submarines, a senior official was cited as saying by Yonhap news agency.

This follows South Korean President Moon Jae In's orders on Monday to push for military reforms to meet the requirements of modern warfare, and to further enhance the military's defence capabilities to counter North Korean threats. He had called for a "new war concept" and an aggressive combat plan.

The Defence Ministry announced on Thursday that it will create a task force on reforms early next month to examine military structure, operations and weapon acquisition. It will aim to draft a plan by year end.