TOKYO, June 26 Reuters A rare unscheduled revision to Japan39;s firstquarter gross domestic product GDP may lead to a sharp downgrade, possibly affecting the central bank39;s growth forecasts and the timing of its next interest rate hike, some analysts say.

The government said on Tuesday it will revise GDP figures for JanuaryMarch to reflect corrections made in construction orders data, and announce the findings on July 1.

Given the big downward revision to the construction orders data, the revised JanuaryMarch GDP figures are likely to show the economy contracted more than expected, some analysts say.

Yoshiki Shinke, senior executive economist at Daiichi Life Research Institute, expects the revision to show Japan39;s economy shrank an annualised 2.7 in the first quarter, much bigger than the current estimate of a 1.8 contraction.

The revision is likely to push down Japan39;s economic growth for the fiscal year that ended in March to 1.0 from 1.2, and may lead to a downgrade in the current fiscal year39;s growth projections including for the Bank of Japan, he said.

What39;s worrying is that the revision could affect monetary policy, by forcing the BOJ to trim its growth projections in fresh quarterly forecasts due at its next meeting on July 3031.

Many economists expect the central bank to hike rates from current levels near zero sometime this year, with some betting on the chance of action at the July meeting.

It could make it somewhat difficult for the BOJ to…