* Aussie shares post biggest weekly gain in over 1-1/2 years
* Banks rally after ANZ’s buyback announcement
* NZ largely unchanged (Updates to close)
June 22 (Reuters) - Australian bank shares rallied after Australia and New Zealand Banking Group doubled its share-buyback programme, but the overall market slipped as trade tensions between China and the United States damaged prospects for export-focussed firms.
The S&P/ASX 200 index fell 0.1 percent or 6.9 points to close at 6,225.2, but still posted its best weekly performance since November 2016 with a gain of 2.2 percent.
South32 Ltd, the world’s largest manganese miner, declined 3.5 percent, while BHP slipped 0.7 percent.
Energy stocks also fell ahead of a key OPEC meeting to discuss output policy later in the day.
Woodside Petroleum Ltd dipped 1.5 percent, while Santos Ltd dropped 3.4 percent.
But financials were bolstered by ANZ announcing its buyback programme would be doubled to A$3 billion ($2.22 billion).
Shares of ANZ firmed 2.9 percent to their highest since March 1, while Commonwealth Bank of Australia rose 1.3 percent to a more than seven-week high.
Across the Tasman sea, New Zealand’s benchmark S&P/NZX 50 index added 0.59 points to finish the session at 8,999.37 and registered a decline of 0.1 percent for the week.
Energy stocks led the gains, with Z Energy Ltd rising 2 percent to a more than five-week high.
Conversely, consumer staples accounted for most of the losses, with dairy firm a2 Milk Company Ltd dipping 1.7 percent. ($1 = 1.3515 Australian dollars) (Reporting by Aditya Soni in Bengaluru; Editing by Simon Cameron-Moore)