Mr Trump chose to skip the summit in Papua New Guinea, leaving the door open for Mr Xi, who arrived two days earlier for a state visit and has been the undoubted star of the show. Later, Pence told reporters he was "very hopeful" the USA and China could reach a deal, but "things have to change" for that to happen.
Xi and Trump are set to meet in two weeks during the G-20 summit in Buenos Aires, a face-to-face laden with high stakes as the United States and China try to settle the escalating trade war.
"We've put tariffs on $250 billion in Chinese goods and that number could more than double", he told CEOs from around the region.
"We have taken decisive action to address our imbalance with China", he said.
China has retaliated with tariffs of its own on US goods.
China has demanded the USA stop deploying ships and military aircraft close to its man-made islands in the disputed waters after American and Chinese ships almost collided near a contested reef in September.
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Trump and Xi are due to meet at a G20 meeting in Argentina late this month, raising some hope that trade tension could ease.
China has also been at loggerheads with the U.S. over its territorial ambitions in the Pacific, encapsulated by Xi's Belt and Road Initiative.
He called numerous projects low-quality ventures that saddle developing nations with loans they can't afford, while saying the U.S.is a better partner.
The spat prompted China, which has repeatedly accused the United States of protectionism, to file a complaint about USA trade practices with the WTO.
We don't drown our partners in a sea of debt, we don't coerce, corrupt or compromise your independence.
"We do not a offer constricting belt or a one-way road", Pence told a summit of APEC chief executives, a precursor to the official leaders' meeting. He announced a Indo-Pacific Transparency Fund, in which the US, Australia and Japan would partner to assist infrastructure funding. Pence is representing Donald Trump at the summits, after the president opted not to attend - becoming the first USA head of state to skip the marquee Asian conferences since 2013.
Xi, who spoke before Pence, anticipated numerous USA criticisms in his speech.
He expressed support for a global free trading system and said nations face a choice of cooperation as unilateralism spreads. He warned against confrontation in the form of a trade war or Cold War.