Negotiations with North Korea have been going on for months
Attention is focused on North Korea amid reports the communist country could today hand over a long-awaited declaration of its nuclear activities.
The declaration, which is six months overdue, should contain full details of its nuclear programme and facilities.
The US has emphasised the information in the document must be verified as correct and complete.
The handover is part of a multilateral deal aimed at disarming North Korea, which tested a nuclear weapon in 2006.
If it did take place, it would be an important milestone - but not the finish line, analysts say.
The declaration is not expected to address the issue of how many nuclear weapons Pyongyang has, and what will happen to them.
A White House spokeswoman said the US was hopeful that the declaration would be produced, but said nothing was definite.
"We just don't know if they're actually going to do it," she said.

Long process
Reports suggest that North Korea will give the document to officials from China, as the host of the multilateral talks process.

There is no information as to where or when the hand-over might take place.
Pyongyang has also invited several media organisations and a senior US State Department official to witness the demolition of a cooling tower at its Yongbyon reactor on Friday, in an apparent show of commitment to the deal.
North Korea agreed in February 2007 to end its nuclear activities in return for aid and political incentives.
It has since closed its Yongbyon reactor, but reaching agreement on the next stage of the deal - the declaration - has proved a tough task.
Thorny issues include whether or not North Korea has a secret programme to enrich uranium for weapons purposes, and whether it has transferred nuclear technology overseas.
If the declaration is produced, the US says it will initiate steps to remove North Korea from its list of state sponsors of terrorism and lift some sanctions.
After that, officials say, the two sides still have to complete the third - and most difficult - part of the disarmament deal.
They must reach an agreement on what happens to any nuclear weapons and weapons-grade material North Korea may have stockpiled.
Not everyone is happy about the way events are moving. Critics in the US accuse the Bush administration of making concessions to North Korea for little return.
Japan, meanwhile, is concerned that any move to de-list North Korea as a terrorism sponsor could marginalise its efforts to find out what happened to Japanese nationals abducted by Pyongyang 20 years ago.