* S&P 500 hits all-time high for sixth straight session
* Conagra soars on quarterly results
* Micron rises after signaling 2020 recovery
* Indexes up: Dow 0.49%, S&P 0.45%, Nasdaq 0.67% (Updates to market close)
By April Joyner
NEW YORK, Dec 19 (Reuters) - Wall Street's major indexes resumed their rally with fresh records on Thursday as U.S. Treasury Secretary Steven Mnuchin said an initial U.S.-China trade deal would be signed in early January.
The benchmark S&P 500 hit a sixth straight all-time high, its longest streak since January 2018, and the Nasdaq ended with gains for the seventh session in a row. The S&P 500, Nasdaq and the Dow Jones Industrial Average all notched record closing highs.
Mnuchin's comments bolstered the optimism that has carried U.S. stocks higher since a trade agreement was announced last week. In an interview with CNBC on Thursday, Mnuchin said the agreement had already been put down on paper and translated, and it would not be subject to renegotiation.
The comments relieved some concerns that disagreements between Washington and Beijing could once again keep the trade deal from being finalized, market analysts said.
"There's still trepidation until we get to the actual signing," said Quincy Krosby, chief market strategist at Prudential Financial in Newark, New Jersey. "That said, because we've gotten some positive comments from both Beijing and Washington, it seems we're likely close to getting a signing of the trade détente."
Further boosting optimism around the strength of the U.S. economy and labor market, data on Thursday showed the number of Americans filing applications for unemployment benefits dropping from more than a two-year high last week.
The market shrugged off U.S. President Donald Trump's impeachment, as the Republican-controlled Senate is widely expected not to remove him from office.
The Dow Jones Industrial Average rose 137.68 points, or 0.49%, to 28,376.96, the S&P 500 gained 14.23 points, or 0.45%, to 3,205.37 and the Nasdaq Composite added 59.48 points, or 0.67%, to 8,887.22.
Conagra Brands Inc shares jumped 15.9% after the Slim Jim maker beat quarterly sales and profit estimates.
Conagra's results also lifted other packaged food makers and helped the S&P 500 consumer staples index advance 0.6%.
Micron Technology Inc shares gained 2.8% after the chipmaker signaled a recovery in its business in 2020 and said it had received licenses to supply some products to Huawei.
Cisco Systems Inc shares rose 2.7% after Barclays upgraded its rating on the networking equipment company's stock.
Advancing issues outnumbered declining ones on the NYSE by a 1.63-to-1 ratio; on Nasdaq, a 1.39-to-1 ratio favored advancers.
The S&P 500 posted 38 new 52-week highs and no new lows; the Nasdaq Composite recorded 134 new highs and 41 new lows.
Volume on U.S. exchanges was 7.08 billion shares, compared to the 6.91 billion average for the full session over the last 20 trading days.
Reporting by April Joyner; Additional reporting by Uday Sampath and Abhishek Manikandan in Bengaluru; Editing by Shinjini Ganguli, Chizu Nomiyama and Diane Craft