* Trump to decide on $300 bln China tariffs after G20 summit
* ECB cuts its growth forecasts for 2020, 2021
* Energy stocks gain as oil prices firm
* AMD rises on Morgan Stanley upgrade
* Dow up 0.29%, S&P rises 0.23%, Nasdaq flat (Updates to early afternoon)
By Medha Singh and Shreyashi Sanyal
June 6 (Reuters) - Wall Street's main indexes edged higher in choppy trading on Thursday, as expectations of a supportive central bank kept in check worries of a flare up in trade tensions after President Donald Trump's fresh China tariffs threat.
Trump said he would decide on more tariffs "probably right after the G20" meeting later this month, which followed his warning overnight to levy duties on at least another $300 billion worth of Chinese goods.
The trade-sensitive industrial sector fell 0.41%, the biggest decliner among the four major sectors lower.
Federal Reserve policymakers have hinted they would be ready to cut rates if the U.S.-China trade spat threatens a decade-long expansion. Since early May, Trump has slapped new tariffs on Chinese imports and warned of U.S. levies on Mexico.
"While the escalation in China is important, the fact that he chose to go after Mexico is more important in fears surrounding trade overall," said Matt Ruffalo, chartered financial analyst at Clarfeld Financial Advisors.
"That's why investor fears regarding trade have heightened but there has been somewhat of an overshadowing by earlier comments around the Fed."
Meanwhile, the European Central Bank's decision not to raise interest rates in the next year led to a flattening of the U.S. Treasury yield curve, which came off its steepest level in seven months the day before.
The ECB also underscored the threat to global economic expansion from the trade disputes by trimming the region's growth forecasts for the next two years.
At 13:08 p.m. ET, the Dow Jones Industrial Average was up 75.13 points, or 0.29%, at 25,614.70, while the S&P 500 was up 6.37 points, or 0.23%, at 2,832.52. The Nasdaq Composite was down 1.93 points, or 0.03%, at 7,573.55.
If current levels hold, the S&P 500 would clock the third straight session of gains.
The energy sector, which was the hardest hit last month by heightening trade tensions, rose 1.21%, the most among the major S&P sectors, as crude prices steadied.
Oil majors Exxon Mobil Corp was up 1.5% and Chevron Corp rose 2.0%.
Advanced Micro Devices Inc rose 6.9%, to the top of S&P 500, after Morgan Stanley upgraded the chipmaker's stock to "equal-weight" from "underweight".
Declining issues outnumbered advancers for a 1.14-to-1 ratio on the NYSE and for a 1.75-to-1 ratio on the Nasdaq.
The S&P index recorded 74 new 52-week highs and four new lows, while the Nasdaq recorded 52 new highs and 124 new lows. (Reporting by Medha Singh and Shreyashi Sanyal in Bengaluru; Editing by Sriraj Kalluvila)