China's militarization of the South China Sea was also a focal point of the meeting.
US Defense Secretary Jim Mattis reiterated this stance on Saturday at the Singapore meeting, saying that the placement of weapons on South China Sea islands "is tied directly to military use for the goal of intimidation and coercion".
"It's an example of the rules-based order in action", she said.
"Vietnam pursues a defensive and peaceful defense policy, does not take sides with one country against another country; does not use force for threaten the use of force", he said.
James Mattis, the United States defence secretary, has denounced Beijing for its "militarisation" of the South China Sea, through which $5 trillion of global trade passes by ship each year.
Satellite photographs taken on May 12 showed China could have deployed truck-mounted surface-to-air missiles or anti-ship cruise missiles on Woody Island in the Paracels of Vietnam.
The two countries, both permanent members of the United Nations Security Council, made the remarks at the Shangri-La Dialogue in Singapore, echoing the latest USA plan to ramp up its freedom of navigation operations to counter Beijing's militarisation in the region and its stance that territorial disputes should be a matter between China and its Asian neighbours.
"For the Chinese it's a matter of national pride", said Collin Koh, maritime security research fellow at Nanyang Technological University in Singapore.
Gen Mattis said the issue of removing U.S. troops from South Korea was "not on the table" and that "our objective remains the complete, verifiable, and irreversible denuclearisation of the Korean peninsula". Airstrips have already been constructed, and in May, China landed nuclear capable bombers on contested islands in the area.
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Super Eagles players during a farewell reception at the Presidential Villa on Wednesday, May 30, 2018. The three-time African champions have been drawn in Group D with Argentina, Croatia and Iceland.
But in a quick pivot, he said the US welcomes cooperation with China "wherever possible", and announced that he has accepted Beijing's invitation to visit there soon.
Despite strong mutual suspicions, the USA had included China in the past two versions of the naval exercise known as Rim of the Pacific, or RimPac, in 2014 and 2016. China protested the maneuver.
House Armed Services Committee Chairman Mac Thornberry, R-Texas, who was attending the conference, said China is alienating other nations and nations must band together and say the actions are unacceptable.
"What we have seen in the last few weeks is just the start, significantly more is being planned", said one Western diplomat, referring to a patrol late last month in which two USA warships sailed near islands claimed by China.
But Chinese Lieutenant General He Lei issued a fiery response, telling the summit that "irresponsible comments from other nations can not be accepted".
China's vice president of the Academy of Military Science, Lt. Gen.
Mattis said the Trump administration's recent decision to disinvite China from a multinational naval exercise this summer was an "initial response" to Beijing's island activity.
He also attacked what he said were excessive loans made under China's Belt and Road Initiative that were binding smaller nations in debt.
Mattis told Asia's biggest security conference Saturday that China's deployment of missile batteries and bombers to outposts in the disputed area was "a reality" the USA and its allies would have to deal with.