Here comes Markit services PMI ...

This morning, we'll get an updated look into the health of the US services sector.

First, at 9:45 a.m. ET, Markit Economics is set to release its services Purchasing Managers' Index (PMI). Economists estimate a reading of 55.

And then, at 10:00 a.m., ISM's non-manufacturing report is due, with the index estimated at 58.2, versus 60.3 in July.

In contrast to manufacturing, the services sector has been a source of relative strength in the US and around the world.

But in Markit's flash release, senior economist Tim Moore quipped that the August reading signaled a "renewed slowdown in US service-sector growth."

BNP Paribas economists wrote in a preview of the ISM report to clients: "Already quite-elevated and after an impressive surge in July, we expect the non-manufacturing ISM to have retraced a bit in August. Consumer confidence declined sharply in July, but rebounded in August, by the Conference Board's measure. While payrolls have slowed a bit, many labor market indicators continue to point to a market that is improving nicely."

We'll update with the latest as the data cross.