* Asian shares flat in early trade, U.S. stock futures down a tad
* China, auto shares take the brunt of Trump's trade war
* Oil prices maintain gains after OPEC agrees on output hike
* Turkish lira rises more than 1 pct after Erdogan's victory
By Hideyuki Sano
TOKYO, June 25 (Reuters) - Asian shares got the week off to a cautious start on Monday amid lingering concerns about escalating trade frictions while U.S. oil prices maintained hefty gains made after major oil producers had agreed on a modest increase in production.
S&P500 mini futures fell as much as 0.5 percent in early trade while MSCI's broadest index of Asia-Pacific shares outside Japan fell 0.2 percent. Japan's Nikkei lost 0.4 percent.
The falls were triggered by a report from Wall Street Journal that U.S. President Donald Trump plans to bar many Chinese companies from investing in U.S. technology firms and block additional technology exports to China.
MSCI's gauge of stocks across the globe has fallen five of the last six weeks, including last week, when it declined one percent - its biggest weekly drop in three months as the threats of trade wars have become all the more real.
Chinese shares were among the biggest losers, tumbling 3.7 percent last week, as Trump put the heat on Beijing, threatening to hit $200 billion of Chinese imports with 10 percent tariffs.
Policy makers in China moved fast to temper any potential economic drag from a trade dispute with the United States, with China's central bank on Sunday saying it would cut the amount of cash that some banks must hold as reserves by 50 basis points (bps).
The reserve reduction, the third by the central bank this year, had been widely anticipated by investors and is aimed to accelerate the pace of debt-for-equity swaps and spur lending to smaller firms.
Another major victim were automaker shares, which shed 4.7 percent last week.
Trump threatened to impose a 20 percent tariff on Friday on all imports of EU-assembled cars, a month after his administration launched an investigation into whether auto imports posed a national security threat.
A senior European Commission official said on Saturday that the European Union will respond to any U.S. move to raise tariffs on cars made in the bloc.
Investors and traders are worried that threats of higher U.S. tariffs and retaliatory measures by others could derail a rare period of synchronized global growth.
Oil prices were supported after OPEC and non-OPEC producers agreed on a modest increase in oil production from next month, without announcing a clear target for the output increase, leaving traders guessing how much more will actually be pumped.
OPEC and non-OPEC said in their statement that they would raise supply by returning to 100 percent compliance with previously agreed output cuts, after months of underproduction.
"In reality, there aren't many countries that can raise outputs, with only Saudi Arabia having the capacity to flexibly increase the output. But if Saudis alone increase outputs sharply, they could face backlash from some other countries," said Tatsufumi Okoshi, senior commodity economist at Nomura Securities.
"So markets seem to be sceptical how much Saudi can increase. We could see some profit-taking after last week's gains but the market will be supported. The next focus will be on the size of output increase by Saudis in July," he added.
U.S. crude futures traded at $68.57 per barrel, little changed for the day after Friday's 4.6 percent rally.
International benchmark Brent fell 2.0 percent, however, to $74.08 per barrel, giving up more than a half of their gains made on Friday.
In the currency market, the euro held firm at $1.1668 , bouncing back after hitting an 11-month low of $1.1508 on Thursday.
The euro climbed on Friday as traders were encouraged by improved regional economic growth data and new assurances by Italian politicians that their nation would not leave the single currency.
Business activity in Germany and France, the euro zone's top two economies, picked up in June despite trade tensions between Europe and the United States, IHS Markit data showed.
The dollar was little moved at 109.93 yen, holding above last week's low of 109.55 yen.
The Turkish lira gained more than one percent on expectations of a stable government after Tayyip Erdogan and his ruling AK Party claimed victory in Turkey's presidential and parliamentary polls on Sunday.
But his victory kept alive worries about inflation and the central bank's independence given Erdogan's recent comments suggesting he wants to take greater control of monetary policy.
The lira traded at 4.6050 to the dollar, compared to 4.6625 at the end of last week.
Bitcoin steadied after hitting seven-month lows during the weekend as the security of cryptocurrency exchange operators came under more scrutiny.
The digital money fell to as low as $5,780 and last stood at $6,155.
Reporting by Hideyki Sano Editing by Shri Navaratnam