WASHINGTON (AP) — U.S. housing starts ticked up just 0.9 percent in July, a sign that higher construction costs might be weighing on homebuilders.

The Commerce Department said Thursday that housing starts last month rose to a seasonally adjusted annual rate of 1.17 million, not nearly enough to reverse the steep 12.9 percent plunge seen in June as rising lumber, land and labor costs appeared to constrain new construction. Lumber prices have shot up by about $7,000 per home since the start of 2017, largely due to tariffs on Canadian softwood lumber by the Trump administration, according to the National Association of Home Builders.

"It looks like U.S. homebuilders are finding it increasingly difficult to get into the groove," said Jennifer Lee, a senior economist at BMO Capital Markets.

Still, housing starts have risen 6.2 percent year-to-date. Solid job growth and a dearth of existing homes for sales have increased demand for new properties.

Prices are also a factor for would-be buyers, who are facing higher mortgage rates this year. The average interest on a 30-year, fixed-rate mortgage was 4.53 percent this week, up from 3.89 percent a year ago, according to the mortgage company Freddie Mac.

Ground breaking fell last month in the two priciest regional markets: the West and Northeast. But starts increased in the more affordable markets of the Midwest and South.

These regional differences caused Stephen Stanley, chief economist at Amherst Pierpont Securities, to suggest that weather might be a source of the slowdown. The West is coping with wildfires and heat waves, while the Northeast dealt with severe rainfalls, he said.

Building permits, an indicator of future construction, rose 1.5 percent in July.

But Robert Dietz, chief economist for the National Association of Home Builders, noted on Twitter that there has been a sharp increase in single-family homes being authorized but never started, which indicates that projects are being delayed because of higher building materials costs.