The Australian share market was marginally weaker at noon as NAB's preparations for an economic downturn weighed down stocks in other big banks.
At 1200 AEDT on Friday, the benchmark SP/ASX200 index was down 7.5 points, or 0.16 per cent, at 4,551.9 points, while the broader All Ordinaries index had backtracked 6.8 points, or 0.13 per cent, to 4,575.1 points.
On the ASX 24, the December share price index futures contract was five points weaker at 4,545 points, with 6,489 contracts traded.
The Australian market closed at a 15-month high on Thursday, following three consecutive days of gains.
But investors were much more cautious on Friday after National Australia Bank announced it would increase its collective provisions by $250 million to $320 million in preparation for an economic downturn.
The flagging of a likely dent in its full-year earnings caused NAB shares to lose 81 cents to $26.15.
CBA shed 39 cents to $56.67, Westpac lost 38 cents to hit $25.58 while ANZ dropped 30 cents to $25.85.
Bell Direct equities analyst Julia Lee said NAB's announcement dragged down other banking stocks, as investors await ANZ's full-year earning announcement on Thursday next week.
'That's having a negative impact for the other banks,' she said.
'It's definitely the banking space that's dragging the market lower.'
Still, banking sector stocks have strengthened by 12 per cent since June, Ms Lee said.
This meant profit taking behaviour, following a run of strong results this week, was the likely cause of Friday's weak equity market performance.
'We've broken that winning streak,' Ms Lee said.
Meanwhile, shares in Australian grains trader GrainCorp have been placed in a trading halt after a potential suitor, Archer Daniel Midlands, requested talks.
Two large parcels of GrainCorp shares changed hands before the start of trade at a price well above Thursday's closing price of $8.85.
National turnover at 1205 AEDT was was 287.752 million securities worth $967 million, with 258 stocks up, 257 down and 272 unchanged.