* World stocks hit highest in 2 1/2 weeks
* U.S. Treasury yields decline after Powell comments
* Trump says "long way to go" on trade; U.S. futures fall
* Euro zone bond yields fall
* Investors remain cautious on trade before Trump-Xi G20 meeting
* Graphic: World FX rates in 2018 tmsnrt.rs/2egbfVh (Updates prices, adds quotes, details)
By Helen Reid
LONDON, Nov 29 (Reuters) - A dovish tone from Fed Chairman Jerome Powell lifted world stocks to their highest in more than two weeks on Thursday, but an uncompromising tone from U.S. President Trump on trade dampened optimism and set U.S. stocks up for a weaker open.
Europe's leading euro zone index gave up some of its earlier gains but remained 0.4 percent higher, with tech, mining and autos sectors - the worst hit by recent losses - scoring the biggest gains.
Wall Street was set for a weaker open with S&P 500 and Nasdaq futures down 0.2 to 0.5 percent after Trump struck an uncompromising tone on trade.
Trump said on Thursday there was "a long way to go" on tariffs with China and urged companies to build products in the United States to avoid them.
"The messaging from the U.S. over the last four weeks has been characteristically erratic," said David Page, senior economist at AXA Investment Managers.
The market is closely watching a meeting between Trump and Chinese leader Xi Jinping at the G20 summit on Saturday at which the leaders are expected to discuss trade.
Investors say a sustained market rally following the summit would hinge on there being substantive concessions from Trump, in particular whether Xi can persuade Trump to postpone a sharp tariff hike on Chinese goods due to take effect Jan. 1.
"If Trump were able to get those additional concessions from China at this meeting, and announce certainly no trade deal, but... a commitment to further negotiations to work towards a deal and in the interim not see further escalation, then that's something markets would latch onto," Page added.
U.S. stocks had enjoyed a strong rally on Wednesday after Powell said U.S. interest rates were "just below" neutral, less than two months after saying rates were probably "a long way" from that point.
"Given the volatility you've seen recently, it's probably quite reasonable to expect a little bit of a bounce. That being said, given the headwinds out there I can't see it being sustained," said Gary Waite, portfolio manager at Walker Crips in London.
Powell's comments briefly pushed the U.S. 10-year bond yield below the psychologically key 3 percent level earlier on Thursday, its lowest level since mid-September.
The yield, which had risen as high as 3.25 percent earlier this month, inched back to 3.02 percent by 1220 GMT.
The dollar, which has outperformed bonds and the S&P 500 this year, benefiting from rising interest rates and safe-haven flows triggered by global trade tensions, fell back after Powell spoke. Following an overnight 0.6 percent slide, it was flat around 96.8 against a basket of currencies.
European bonds too rallied across the board, with German 10-year yields hitting a three-month low of 0.322 percent, down 3 basis points on the day.
Italy's borrowing costs slipped too, with 10-year yields dipping around 2 bps. A bond auction enjoyed much better buying interest than at last week's deal targeting retail investors as the government has shown signs it could compromise with the European Union on its budget deficit target.
Debt costs at the auction fell to their lowest in two months, with 10-year yields at 3.24 percent, down from 3.36 percent at October's auction, while five-year yields tumbled 23 bps versus last month.
Italy's yield spread over Germany -- effectively the premium investors require to hold Italian risk -- tightened to 290 bps .
On currency markets, the euro edged 0.2 percent higher at $1.1370 after advancing 0.7 percent the previous day.
Sterling lost 0.4 percent to $1.2771 against the dollar after Bank of England Governor Mark Carney warned a disorderly Brexit could trigger a worse economic downturn for the UK than the financial crisis.
In commodities, oil prices reversed course and rose after sources said Russia had accepted the need for cuts in production together with OPEC.
Brent crude LCOc1> rose 51 cents to $59.27per barrel. It has slumped 21 percent this month, during which it fell to a 13-month trough of $58.41.
Emerging market stocks hit a three-week high, with the index up 0.7 percent as investors bought back into risky assets. An index of emerging currencies surged 1.4 percent to a 10-day high.
Reporting by Helen Reid, additional reporting by Abhinav Ramnarayan; editing by Larry King and Toby Davis