The United States and Japan are "very close" to reaching a bilateral agreement seen as vital for sealing the 12-country Trans-Pacific Partnership trade deal, a former economic adviser to U.S. President Barack Obama says.

Matthew Goodman, an expert on Asian economic matters at the Center for Strategic and International Studies, an influential U.S. think tank, also said in a recent interview that there are expectations for a bill granting Obama "fast track" authority to sign trade deals could clear Congress "within a few weeks."

After the summit between Obama and Prime Minister Shinzo Abe on Monday, the leaders "indicated that they made significant progress," said Goodman, former White House coordinator for Asia-Pacific Economic Cooperation. They are now likely focused on trying to get the other TPP members to quickly work toward concluding an overall deal, he added.