(Adds data on corporate profits, sales)

* Q2 capex +1.5 pct yr/yr, seasonally-adjusted -2.8 pct m/m

* Suggests downward revision to revised Q2 GDP data out Sept. 8

* Recurring profits +22.6 pct yr/yr, showing solid gains

By Stanley White

TOKYO, Sept 1 (Reuters) - Japanese companies curbed their pace of investment in plant and equipment in April-June, suggesting the government will revise down its initial rosy estimate of economic growth for the second quarter.

Capital expenditure in April-June rose 1.5 percent from the same period last year, slower than a 4.5 percent annual expansion in January-March, hit by a decline in spending by auto makers and manufacturing equipment makers.

Excluding software, capital expenditure fell 2.8 percent from the previous quarter on a seasonally-adjusted basis, versus a downwardly revised 0.9 percent increase in January-March, finance ministry data showed on Friday.

A preliminary estimate showed Japan's economy grew by an annualised 4.0 percent in April-June, which analysts believed to be due to a long awaited pick-up in domestic demand.

But the slowdown in capital expenditure suggests this could be revised down to around 3.0 percent, which could weaken confidence in the government's economic policies and the business outlook.

"Many companies want to invest, but they realise that the potential growth rate is very low, so they don't want to invest excessively," said Hiroaki Muto, economist at Tokai Tokyo Research Center Co.

"This is a GDP downgrade. We are looking at annualised growth above 3.0 percent, but it's not all bad because we still have exports and industrial output."

Revised gross domestic product (GDP) for April-June is due on Sept. 8 at 0850 JST (2350 GMT Sept. 7).

The initial reading of 4.0 percent annualised growth was the fastest pace in more than two years.

Some economists have said that pace is unsustainable, and the economy is likely to slow in the current quarter.

While the capex figures suggested corporate caution, sales and profit growth in the quarter was robust.

In April-June, operating profits at Japanese companies rose 22.6 percent from the same period a year ago to a record high of 22.3 trillion yen ($202.65 billion), driven by higher earnings for makers of autos, industrial chemicals, and electronics.

Sales rose an annual 6.7 percent, faster than the 5.6 percent gain in January-March and showing that the corporate sector is in good health.

Many economists remain optimistic that the economy can continue to grow, but recent economic data paint a mixed picture.

Household spending unexpectedly fell in July, but growth in retail sales slowed less than economists expected.

Industrial output fell more than expected in July, pulling back from the previous month's gain, but manufacturers forecast factory output would rebound in August, underscoring the view that the economy will continue to grow. ($1 = 110.0400 yen) (Reporting by Stanley White; Editing by Kim Coghill)