President Donald Trump said the United States would delay increasing tariffs on $250 billion worth of Chinese imports, after Beijing exempted some US goods from additional levies.
Trade-sensitive technology stocks provided the biggest boost among the 11 major S&P 500 sectors, taking the benchmark index just 0.3pc off the record-high hit in July.
While most analysts agreed that the concessions were a step in the right direction, they were skeptical that the moves would lead to a breakthrough in trade negotiations between the world's two largest economies.
"Both China and the United States are trying to reach across the aisle ... but all they've done is kick the can further down the road," said Paul Nolte, portfolio manager at Kingsview Asset Management in Chicago.
ECB chief Mario Draghi pledged indefinite asset purchases on Thursday and cut deposit rates to a record low for the first time since 2016.
The move took a toll on US treasury yields across the board, which dragged down shares of banks by 0.6pc.
Investors expect other central banks to deliver similar stimulus programs to prop up a global economy that has been bruised by the Sino-US trade war.
The Federal Reserve is also expected to reduce interest rates at its policy meeting next week.
All the major indexes hit a session high on a report that the Trump administration was considering an interim deal with China.
However, they quickly pared gains after CNBC said that a senior White House official denied the report.
"It's just what we should come to expect now," Kingsview's Nolte said about the choppy market reactions.
Separately, data on Thursday showed US underlying consumer prices in August recorded the largest annual gain in a year, while weekly jobless claims dropped to a five-month low.
At 13:50 a.m. ET, the Dow Jones Industrial Average was up 155.02 points, or 0.57 percent, at 27,292.06, the S&P 500 was up 18.54 points, or 0.62 percent, at 3,019.47 and the Nasdaq Composite was up 53.61 points, or 0.66 percent, at 8,223.29.
Energy stocks fell 0.44pc and were the only decliners among the 11 major S&P 500 sectors as oil prices dipped after a meeting of the OPEC+ alliance yielded no decision on deepening supply cuts.
Industrial stocks were pressured by drops in Deere & Co and Caterpillar Inc after Wells Fargo downgraded their shares to "market perform".
Oracle Corp fell 3.7pc after the software maker posted first-quarter revenue that missed Wall Street expectations and said Chief Executive Officer Mark Hurd would be taking a medical leave.
Advancing issues outnumbered decliners by a 1.32-to-1 ratio on the NYSE and a 1.23-to-1 ratio on the Nasdaq.
The S&P index recorded 39 new 52-week highs and one new low, while the Nasdaq recorded 79 new highs and 20 new lows.