There are signs of improvement in the economy, but credit is the iceberg that still looms over the U.S. commercial construction sector as it begins to regain maneuverability, the National Association of Realtors' chief economist says.

Speaking to the organization's Economic Issues and Commercial Business Trends Forum, Lawrence Yun said consumer spending is slowing rising, jobs are slowly growing. However, he said, “Realtors have reported that they typically obtain commercial mortgages from smaller banks.

"They find it frustrating that the larger banks are gaining market share at the expense of smaller sized lenders, which is hampering lending to small businesses.”