SINGAPORE, May 19  -- Market access remains the most difficult part of the ongoing Trans-Pacific Partnership (TPP) talks, which are set to take "a bit of time," ministers involved in the talks said here on Monday.

Speaking at the end of the first day of the two-day TPP ministerial meeting in Singapore, New Zealand's Minister of Trade Tim Groser said that he is comfortable with the progress.

"The rules negotiation is in a very advanced stage. I'm very comfortable with the direction of travel," he told reporters.

However, on the market access issue, which is the other pillar of the TPP talks, the United States and Japan have been in tough talks over access to Japan's agricultural market and the United States' automobile market.

Groser said that there is no progress yet between the top two economies of the bloc on market access but that they have now started to engage each other on the details.

"This negotiation is never designed for anyone who is into instant gratification. This is going to take a little time, but we are absolutely moving forward, in my opinion, but we are not there yet," he said.

The TPP talks led by the United States gathered the representatives of 12 countries that also include Australia, Brunei Darussalam, Canada, Chile, Japan, Malaysia, Mexico, New Zealand, Peru, Vietnam and Singapore.

Prior to the meeting, chief negotiators and subject matter experts have met in Vietnam from May 11 to May 17, Singapore's Ministry of Trade and Industry said in a statement.

The last ministerial meeting of the TPP talks took place in February. The ministry said that the ministers "agreed on the majority of the landing zones identified at the meeting in December."

The ministers have said that the two-day ministerial meeting in Singapore are a "check-in meeting" aimed at evaluating the progress.

"The main task is to see what is the state of the negotiations after two more rounds of the TPP (talks) and the various bilaterals. They need to assess where they have moved far enough to be able to close sections that have been unfinished and what remains to be done," said Deborah Elms, head of Temasek Foundation Center for Trade and Negotiations, Nanyang Technological University.

Akira Amari, a Japanese minister in charge of the negotiations, said at the end of Monday that he and U.S. representative Michael Froman had bilateral meetings to affirm the drive to push for progress before a plenary session.

Amari said he told other ministers at the meeting that Japan will try its best to open the market even though it cannot open its agricultural product fully.

"Only in this way can Japan contribute to the high standards set by the TPP," he told reporters in Japanese.

Elms said she believed the talks to be still stuck on the same issues -- "the last few agricultural items and autos."

"The problem is that Japan has promised to open the market and yet to protect sacred sectors," she said in an email to Xinhua.

The United States had pushed for the conclusion of the talks by the end of last year on the TPP, a comprehensive and demanding but controversial trading pact that covers not only free trade but also aspects such as stringent intellectual property rights, the rights of multinationals to sue national governments and what the United States view as unfair competitive advantage of state-owned enterprises. Some of the observers have said that the TPP talks are more on fair trade than on free trade.

Groser said market access is always going to be the hardest part of the negotiations.

The market access issue between the United States and Japan are bilateral but has to be multilateralized, too. Japan also had bilateral talks with several other countries on Monday.

"We are dealing with things that have left aside after some 60 or 70 years of multilateral negotiations, and there are enormous tariff and other barriers left in some of these areas," Groser said.

The United States has yet to get the "fast track" so that it has the authorization to negotiate the terms and put them to the congress for vote without the need for amendments.

Groser said that it is not practical to set timeline.

Elms said that since the talks have not yet concluded now, the next likely date is November 10, which is after the APEC meeting and before the mid-term elections in the United States.