Countries involved in negotiations for the Trans-Pacific Partnership began talks in Ho Chi Minh City on Monday, aiming to strike a deal in time for a ministerial meeting Singapore will host from May 19 to 20.

The fresh round of negotiations comes after Japan and the United States, the two biggest economies in the TPP talks, made progress in solving bilateral contentious issues after the summit between Prime Minister Shinzo Abe and President Barack Obama last month.

Over the next four days, the chief negotiators from the 12 TPP members will focus on resolving tough remaining issues, such as tariffs — especially in areas including politically sensitive agricultural goods, intellectual property and reform of state-owned companies.

Koji Tsuruoka, Japan's top TPP negotiator, said bilateral negotiations over tariff removal will be the key to moving the meeting forward.