US President Barack Obama and Japan's Prime Minister Shinzo Abe are due to meet to discuss a significant trade deal for the Pacific Rim.
The Trans-Pacific Partnership (TPP) agreement is aimed at liberalising markets in 12 countries, and the US and Japan are among the biggest players.
The discussion comes amid a week-long state visit to Washington by Mr Abe.
Earlier in the visit the two leaders agreed on new guidelines on the two countries' defence co-operation.
The TPP is poised to be the world's largest-ever free trade deal, and estimates suggest the proposed deal could cover up to 40% of global trade.
Besides the US and Japan, other countries involved in the deal are: Brunei, Malaysia, Vietnam, Singapore, Australia, New Zealand, Canada, Mexico, Chile and Peru.
The deal has been in the making for about a decade. Both leaders have advocated for the partnership, arguing that freer trade will benefit their economies, but critics in their respective countries fear that jobs and certain industries will be made more vulnerable.
Mr Obama is seeking Congress' guarantee to "fast-track" approval for the deal.
Air base relocation
Both countries also recently agreed on new defence guidelines which clarify the US' commitments to Japan's security.
US Secretary of State John Kerry said the US commitment to Japan remained "iron-clad" and covered all territories under Tokyo's administration, including islands in the East China Sea which Beijing also claims.
The new guidelines also build on Japan's resolution last year to reinterpret its pacifist constitution and take on a more assertive military role, allowing Japan to defend the US and other allies.
Japanese television network NHK said Mr Abe is expected to discuss those guidelines with Mr Obama on Tuesday, as well as the controversial relocation of the Futenma US air base in Okinawa.
The central government is currently in a stand-off with local government on plans to shift the Futenma air base from a highly-congested part of Okinawa to Nago, in the north of the island.
Residents fear damage to environment and associate US camps with accidents and crime.
But Mr Abe is expected to say that Japan will go ahead with the relocation and ask for US co-operation in easing the local burden of hosting US troops, said NHK.
On Tuesday, Japanese police said they were investigating a possible attack on another US air base near Tokyo.
Residents reported hearing explosions near Camp Zama and police found pipes and projectiles in a nearby field. No injuries were reported.