The most worrisome number in Friday's disappointing U.S. employment report may be 6,600.

That is the net number of jobs that retailers cut in May, contributing to a far weaker-than-expected reading on private sector payrolls.

Economists knew May's employment figures would be skewed by a government hiring spree to fill temporary census jobs, and in that respect there was no surprise. Census jobs accounted for 411,000 of the net gain of 431,000.

But there was hope that private employers would step up. Economists polled by Reuters thought there would be a gain of 190,000 private-sector jobs last month. Instead, it was just 41,000.

The decline in retailing jobs, the first monthly drop since December, is the latest evidence that consumer spending may be stagnating after a surprisingly strong start to the year.

Major U.S. retailers reported lackluster sales on Thursday, and some companies have warned of softening demand, a troubling sign for a country that counts on consumers for two-thirds of economic activity.

If that trend continues, it suggests that second-quarter economic growth may be even slower than the 3.0 percent annualized pace recorded in the first three months of the year. That was already a marked slowdown from the fourth quarter.

As for those census workers, their temporary jobs will probably be finished in July. While they are not expected to swell the weekly jobless claims data, they will keep pressure on the unemployment rate.

The jobless rate ticked down to 9.7 percent in May from 9.9 percent in April, but may not fall much further before U.S. congressional elections in November. That does not bode well for President Barack Obama, who is likely to see his Democratic party lose more seats.

(Reporting by Emily Kaiser)