South Korea doesn't need to feel pressed for time in deciding whether to join the ongoing Trans-Pacific Partnership (TPP) negotiations, a top U.S. trade official said Wednesday.

"There's no formal deadline," Acting U.S. Trade Representative Demetrios Marantis said at a press conference for foreign journalists in Washington. "The idea is that if economies aren't ready right now, that they'll be able to join once it's done and essentially accede to the TPP."

Marantis said an envisioned TPP deal would be a "living agreement."

The U.S. aims to complete the TPP negotiations by the end of this year as part of its broader efforts to intensify its engagement with Asia and create jobs at home.

The pact is being negotiated by 11 nations: U.S., Australia, Brunei, Canada, Chile, Malaysia, Mexico, New Zealand, Peru, Singapore and Vietnam.

Japan announced its intention to participate in the talks last week.

The U.S. hopes to wrap up the multilateral talks before the Asia-Pacific Economic Cooperation summit in Bali in early October, according to a source.

Once a deal is reached on common issues, each nation can have bilateral talks if necessary, added the source.

"The whole point of the agreement is to serve as a platform for regional integration in Asia," Marantis said. "The idea of it is to be a living agreement so that we're able to incorporate new members and new issues as we look to the future."

U.S. officials describe South Korea as a "natural candidate"

for the TPP, given Washington and Seoul have a high-standards, one-on-one free trade agreement in place.

South Korean officials said they are exchanging related information with the U.S. for review of expected gains and losses.

"As South Korea is focusing on continuing to implement the South Korea-U.S. FTA smoothly, it is not in a hurry for the TPP," another source said.

Speaking at the Foreign Press Center, meanwhile, Marantis faced several questions on the possibility of China or Taiwan joining the TPP talks.

He maintained a cautious stance, reiterating the U.S. and its current dialogue partners do not "invite" countries or economies to join.

"It's the reverse," he said. "If an economy is interested in meeting the high standards of the TPP agreement, it needs to, you know, express that interest, that it's capable of meeting the high standards that we're negotiating, and the 11 TPP partners then decide by consensus whether or not to admit a new member."

If China, Taiwan, the Philippines or Thailand want to take part in the talks, he added, "it's incumbent upon those economies to be able to convince the other TPP partners that they are capable of meeting the high standards that we're negotiating."

Marantis, who was named deputy trade representative in 2009, has been serving as acting chief since Ron Kirk left the office last week.

He is said to be among the strong candidates to become Kirk's successor, having served as chief international trade counsel for the Senate Finance Committee before joining the administration. (Yonhap News)