However, news of the first phase of the deal last week has failed to yield any concrete details so far, while officials from both sides have also warned that much more work needed to be done before an accord could be agreed.
Singapore's index fell as much as 0.7% during the day, marking its worst session in more than a week. It ended 0.3% lower. Industrial stocks accounted for most of the losses on the local benchmark index, with Jardine Strategic Holdings shedding 1.5%.
Singapore's non-oil domestic exports (NODX) shrank for a seventh consecutive month in September owing to a slump in electronics shipments, a key driver of growth, data released earlier in the day showed.
"With year-to-date NODX growth contraction already averaging close to 10% yoy, the full-year 2019 NODX growth may potentially mark the worst NODX contraction since 2009 post-GFC (global financial crisis)," OCBC said in a note.
Singapore's Prime Minister Lee Hsien Loong also said the city-state's economy would be lucky if GDP growth is above zero this year as it faces uncertain times due to the Sino-US trade war. Among other Southeast Asian markets, Vietnam stocks dropped to its lowest level in two weeks, dented by losses in the real estate and financial sectors. Joint Stock Commercial Bank for Foreign Trade of Viet Nam and real estate developer Vingroup JSC lost 1.1% and 0.9%, respectively.
The Thai benchmark snapped a three-day gaining streak, weighed down by energy stocks. PTT Pcl, the country's largest energy firm and PTT Exploration and Production Pcl slipped 1.7% each.
Meanwhile, Philippine stocks hit their highest level in more than four weeks, buoyed by gains in the financial sector. Metropolitan Bank and Trust Co and Bank of Philippine Islands rose 1.2% and 1.1%, respectively.
Indonesia stocks extended gains for a fifth straight day, with consumer shares providing the biggest boost to the local benchmark index.