(For a live blog on the U.S. stock market, click or type LIVE/ in a news window.)
* Pinterest plummets as 2019 forecast disappoints
* U.S. agrees to lift metal tariffs on Canada, Mexico
* Energy shares fall on weak oil prices
* Luckin Coffee surges in market debut
* Dow up 0.26%, S&P flat, Nasdaq down 0.19% (Updates to early afternoon)
By Amy Caren Daniel and Sruthi Shankar
May 17 (Reuters) - U.S. stocks struggled for direction after three days of gains on Friday, as investors weighed mixed headlines on trade, with China's aggressive stance in its trade war with the United States remaining an overhang.
After opening down 0.75%, the S&P 500 erased some losses after media reports that the United States was close to a deal to remove tariffs on steel and aluminum imports from Canada and Mexico.
"That is a piece of positive news. The original tariffs were on steel and aluminum and that is what started this whole trade war," said Art Hogan, chief market strategist at National Securities in New York.
Upbeat economic data, which showed U.S. consumer sentiment jumped to a 15-year high in early May, kept the market sentiment buoyant.
However, the focus remained on the growing U.S-China rift, which has taken a toll on global financial markets.
The ruling Communist Party's People's Daily wrote on Friday the trade war would only make China stronger and never bring the country to its knees.
Beijing's higher tariffs on $60 billion worth of U.S. products will take effect on June 1, which could prompt Washington to go ahead with tariffs on a further $300 billion worth of Chinese goods.
Uncertainty around trade led farm equipment maker Deere & Co to cut its full-year forecast, sending its shares down 6.3%.
The drop in shares of Deere as well as Caterpillar Inc and 3M Co pressured the tariff-sensitive industrial sector.
Energy stocks declined 0.6%, the most among the major S&P sectors, as oil prices fell.
Applied Materials Inc gained 4.8% after the chip gear maker's upbeat third-quarter profit eased concerns about waning chip demand.
At 13:17 ET the Dow Jones Industrial Average was up 66.06 points, or 0.26%, at 25,928.74, the S&P 500 was up 1.99 points, or 0.07%, at 2,878.31 and the Nasdaq Composite was down 15.06 points, or 0.19%, at 7,882.99.
Under Armour Inc rose 7.8% after JP Morgan upgraded the sports wear maker to "overweight" from "neutral".
Online scrapbook company Pinterest Inc slumped 10.8% after the recent Wall Street debutant forecast 2019 revenue broadly in line with Wall Street targets.
Luckin Coffee Inc's shares, the Chinese challenger to Starbucks Corp, surged 23.6% in their market debut.
Declining issues outnumbered advancers for a 1.84-to-1 ratio on the NYSE and a 1.73-to-1 ratio on the Nasdaq.
The S&P index recorded 25 new 52-week highs and five new lows, while the Nasdaq recorded 49 new highs and 85 new lows. (Reporting by Amy Caren Daniel, Sruthi Shankar and Shreyashi Sanyal in Bengaluru; Editing by Shounak Dasgupta and Arun Koyyur)