CANBERRA - Singapore and Australia are good friends, and this partnership is part of a network of relationships among countries in the region that lends it stability, Prime Minister Lee Hsien Loong said on Thursday (Oct 13).

"We are collaborating to build an open and inclusive regional security architecture, working to keep international trading open and to enhance regional trading arrangements like the Trans-Pacific Partnership (TPP) and Regional Comprehensive Economic Partnership (RCEP)," he said at a press conference after witnessing the signing of four Comprehensive Strategic Partnership (CSP) agreements.

He added: "Not everybody is in on every arrangement, but collectively the arrangements add up to a constructive and robust network of cooperation and architecture."

Responding to a question about whether the CSP, especially its newly-deepened defence ties, could make Singapore and Australia threaten other nations in the region, Mr Lee said: "We've been friends for a very long time, I don't think Singapore and Australia together could possibly be seen as a bloc."

Noting that China is the largest trading partner for both nations, he said Singapore and Australia are "good friends, but we are not treaty allies and neither are we opposed to any countries in the region."

As for another major power, the United States, Mr Lee said it remains a "valuable and important partner to us."

The Seventh Fleet - the American fleet based in Japan since World War 2 - is important, he said. "That has been so since the war, and it remains so."

But it was also just as important that the US ratify the TPP soon, he added.

Mr Lee later said in a separate interview with local media he was concerned about both the US presidential candidates' lack of support for the TPP in its present form: "We still hope it will pass, hopefully before January when the new administration takes over."

Echoing his views, Australia's Prime Minister Malcolm Turnbull said that the US' presence in the region has been "the foundation of our prosperity for the last 40 years."

"And that extraordinary growth, perhaps most of all in China, has been underpinned by that foundation of peace," he said, adding that it goes beyond "fleets and navies" and requires the ratification of the TPP by the US.

Mr Lee had also underscored the need for good relations between the US and China, and US and Japan, which would give them a platform to discuss difficult issues like the South China Sea.

As for Singapore's interests the issue, these remain its concerns over the "freedom of navigation, international law such as the United Nations Convention on the Law of the Sea (Unclos), the stability and peace of the Southeast Asian region, and the relevance and centrality of Asean."

"Those have not changed," he said.

The prime ministers were also asked about the message the CSP is sending out, especially at a time when some governments are pushing for protectionist measures or are reluctant to turn to innovation or automation.

Said Mr Lee: "The signal to the world is that... we found opportunities to cooperate together, we are very happy we are making progress, and we hope that you too will find it possible to make similar progress with us or with each other."

There will be problems, but it's "far better we cooperate together than (closing) ourselves off in our own little corner, because that way leads to impoverishment, leads to misunderstanding leads to trouble," he said.

Mr Turnbull added that it was critical for leaders to reassure, but also explain, to the community that "turning your back on change is only a road back to impoverishment."

"We need to embrace... change and innovation because we know that's the way to secure the jobs and the growth, not just for our generation, but for our children and grandchildren," he said.

Earlier, Mr Lee and Mr Turnbull witnessed the signing of four agreements, the first tranche of initiatives under the CSP. They cover deals on trade, defence, science and innovation, as well as efforts to combat transnational drug crime.

At the press conference, PM Lee said there were trade-offs in the negotiation process: "There will be sensitive issues for both sides which we have to consider carefully. For example, if you're talking about armed forces training, there's a question of sovereignty and what are the arrangements that will be made specific ally so that problems don't arise."

But he added it was also a matter of understanding the other side's needs and considerations.

"These are win-win deals and the art of negotiation - you bargain hard, but you bargain to win together."

On whether Singapore could be assured that Australia's bipartisan system can sustain the CSP through the years, Mr Turnbull quipped: "So profound was the spirit of bipartisanship yesterday that the Leader of the Opposition (Bill Shorten) and I attended the events wearing the same orange ties. It shows it was almost subliminal - the spirit of harmony."

In a joint statement issued later, the two leaders reiterated their nations' "natural" partnerships, given their common interests and desire for a prosperous and stable region.

They commended the sustained efforts of both nations to realise the benefits of closer cooperation, particularly in trade and investment, innovation and science, defence and security and people-to-people links.

"Together, the agreements signed this week represent the most substantial upgrade in the Australia-Singapore relationship in a generation," it said.

It added: "The Prime Ministers looked forward to further talks in Singapore in 2017, and tasked Ministers and officials with continuing to work closely to advance the initiatives agreed under the Comprehensive Strategic Partnership."

Mr Lee also met with Opposition Leader Bill Shorten, and will call on Governor-General Peter Cosgrove later on Thursday before heading home.