Japanese Prime Minister Shinzo Abe pledged to deliver "all possible steps" if risks to the economy intensified, signalling a fiscal-stimulus boost in the event this month's sales tax hike triggers a sharp downturn in growth.

The government rolled out a twice-delayed rise in the sales tax to 10% from 8% on Tuesday, a move that is seen as critical for fixing the country's tattered finances. But there are fears the higher tax could hurt consumer spending and tip the economy into recession.

This has led to speculation that Tokyo will step up fiscal spending, though it has already taken measures to mitigate the pain on consumption, mindful of the severe economic downturn that followed the last increase in the sales tax in 2014.

"Achieving economic growth remains my administration's top priority," Abe said in a speech delivered to an extraordinary parliament session.

"If downside risks materialise, we will take all possible steps flexibly and without hesitation to ensure the economy is on a growth path," he said.