South Korean President Lee Myung-bak is expected to outline his country's latest position on the crisis with North Korea at a major Asian security conference in Singapore.
US Defence Secretary Robert Gates said on his way to the conference that the US and South Korea were looking at increasing their joint manoeuvres.
The crisis erupted over North Korea's alleged attack on a South Korean warship in March which left 46 dead.
Pyongyang denies responsibility.
The run-up to this major security conference has been overshadowed by the crisis and tensions are clearly still running high.
It is by chance that the South Korean president is scheduled to open the conference with the keynote address.
Mr Gates said before he arrived in Singapore that Washington and Seoul were looking into holding additional military manoeuvres in response to the sinking, to reassure Seoul.
He described North Korea as "more unpredictable than usual".
The defence secretary also suggested US-Chinese military relations are still cool - and blamed Beijing's military leadership.
The US-China relationship is both crucial and complicated.
It has been through a bad patch recently, not least over tensions surrounding the latest plans for US arms sales to Taiwan.
But there have been signs of a warming of ties again, at least on the political front. Not so, though, on the military front, according to Mr Gates.
He said he believed China's military leadership was "significantly less interested" in developing the relationship than the political leadership.
He also suggested that this had complicated the handling of the aftermath of the sinking of the South Korean vessel.
American officials had apparently hoped that Mr Gates' visit to the region might be an opportunity to improve military-to-military contacts again.
But Beijing apparently turned down the idea of a visit there by the defence secretary as part of his trip - although other top US officials, including Secretary of State Hillary Clinton have visited Beijing recently.
It is another cloud overshadowing this gathering of political leaders, defence officials, and military top brass.
So is the political fallout in Japan over the tensions surrounding the future of US military bases on Okinawa.
The conference itself, known as the Shangri-La Dialogue, and organised by London-based think tank the International Institute for Strategic Studies, has taken on increased significance over the years.
In a region that lacks an overall international defence and security framework, it has become a major annual event on the security calendar.
As well as the South Korean president and the US defence secretary, this year's attendees include the defence ministers of Japan, South Korea, Britain, Australia, Singapore, Malaysia, Indonesia, and Vietnam, Russian Deputy Prime Minister Sergei Ivanov and the deputy chief of the Chinese general staff.