Here come ADP private payrolls ...

The ADP Research Institute will release its monthly report on private-sector employment in the US at 8:15 a.m. ET.

Economists estimate that the report will show private payrolls grew by 175,000 in August, according to Bloomberg.

As usual, this release precedes the government's non-farm payrolls numbers on Friday.

Both take on added importance right now because of the Federal Reserve, which has become more vocal about its plans to raise interest rates again soon.

Strong employment in August would complete a "hat trick of stellar jobs reports," the third consecutive strong month, wrote Craig Erlam, senior market analyst at Oanda.

"Two excellent jobs reports in June and July have put a rate hike this year well and truly back on the table but it would seem that investors want at least one more in order to be convinced," he said in a note on Wednesday. "While December may now be marginally priced in for a hike, a weak jobs report could quickly change that."

More to come ...