The Dow Jones and S&P 500 rose to record highs on Wall Street last night following a volatile session marked the signing of the long-awaited US-China trade agreement.
The Dow Jones gained 0.3% to finish at 29,030 and the broad-based S&P 500 added 0.2% to 3,289.
Analysts said the choppy trading session reflected worries about lofty US stock valuations following the market's surge since the fall.
"We've been on a tear since mid-October," said Briefing.com analyst Patrick O'Hare, who said investors likely will wait for more earnings reports from big companies before moving significantly further.
"It's going to take a lot of good new news to get the market to take another leg higher," he said.
The trade deal between the world's dominant economic powers called off some US tariffs that had been planned on Chinese goods, and obliged China to beef up purchases of American crops and other exports and provide intellectual property protections for US technology.
Investors have cheered the deal following nearly two years of conflict in which US-China trade tensions occasionally flared, pressuring stocks.
But Oxford Economics described the agreement as a "fragile truce".
It warned that "while the deal is a step in the right direction, further tariff rollbacks should not be expected until after the elections, and broken promises could lead to tariffs snapping back in the coming months."
Among individual companies, Goldman Sachs dipped 0.2% as it reported lower fourth-quarter due in part to a one-time charge of $1.1 billion for legal costs connected to probes into the bank's role in the 1MDB scandal.
Among other companies reporting results, Bank of America fell 1.8% and United Health Group gained 2.8%.
Target plunged 6.6% after the big-box retailer reported disappointing sales for the critical Christmas shopping season.