* Nikkei rebounds but posts second straight week of fall
* Sony jumps 10% on share buyback, Microsoft partnership
* Communication equipment makers gain on rally in U.S. peers
* Investors look to Monday's GDP, sales tax debate
By Hideyuki Sano
TOKYO, May 17 (Reuters) - Japan's Nikkei share average jumped on Friday, led by Sony and technology shares, but ended the week with a slight loss amid concerns about rising U.S.-China trade tensions.
The Nikkei rose 0.89% to 21,251 points. For the week, it was down 0.44 percent, the second straight week of losses. The broader Topix rose 1.09% to 1,554.25, eking out weekly gain of 0.3%.
Markets gave back some earlier gains amid increasingly tough words from China on trade. The Communist Party's People's Daily used a front-page commentary to evoke the patriotic spirit of past wars, saying the trade war would never bring China down.
Sony jumped 9.9% after it announced a share buyback and strategic partnership with Microsoft Corp on areas such as streaming games, media and new image sensors.
Softbank Group, a major investor in a whole gamut of U.S. tech firms, gained 2.3%.
Some communication equipment manufacturers rose after upbeat earnings boosted Cisco 6.6%, helping to drive up the Nasdaq Telecommunication index 4.2%, the second biggest gain in the past four years.
Some market players suspect those shares also were helped by speculation of possible windfalls from Washington's tough stance on China's Huawei Techonologies, by far their strongest rival.
NEC rose 2.3% while Fujitsu gained 0.5%. On the other hand, Murata Manufacturing, a Huawei supplier, extended losses, falling 0.7%. Murata has plunged 19% so far this month.
"I think Japanese share markets will remain capped for now, given the perception that (they) will be susceptible to foreign demand and vulnerable to trade tensions," said Hiroyuki Ueno, senior strategist at Sumitomo Mitsui Trust Asset Management.
Investors also looked to Japan's GDP data due on Monday, which is expected to show the country's economy contracted slightly in the first three months of this year. Signs of deeper weakness could prod the government to delay a sales tax hike slated for October.
Japanese corporate earnings have been weaker than expectations as the economy has stagnated.
A case in point was brokerage shares index, which hit its lowest level since August 2016 before recovering to positive territory.
Industry leader Nomura Holdings fell 0.6 percent to hit near-three-year low. (Editing by Kim Coghill)