US crude steel output increased by only 5,000 st, or 0.3%, last week after a collective gain of nearly 54,000 st over the previous three weeks, the American Iron and Steel Institute said Monday, but the slight gain was enough for a new 2011 weekly high.

Crude steel output totaled 1.888 million st in the latest week, compared with 1.883 million st a week earlier -- but the weekly total was the most so far this year. Crude steel production has increased in five of the past six weeks, according to the Washington-based trade group, albeit in very small increments.

The capacity utilization rate for all US mills strengthened to an estimated 77.2% last week, compared with 75% three weeks ago, according to AISI's estimates.

For the 33-week period that started January 1 and ended August 20, total crude steel output in the US was up about 6% to 60.5 million st compared with 57.1 million st a year ago. The utilization rate this year has averaged about 74.7%, according to the AISI survey.

In the latest survey week, steel production in two key regions of the country decreased, while production increased in most other regions.

Steel production in the Indiana/Chicago area decreased by about 1% on the week to 470,000 st, and steel mills in the Midwest region lost about 1.4% to 272,000 st.

Meanwhile, steel output in the South -- the country's largest steel-producing region -- increased 0.5% on the week to 629,000 st, compared with 626,000 st a week earlier.

These three regions accounted for an estimated 73% of the country's total steel production last week.

Among other regions, Pittsburgh/Youngstown produced 145,000 st, down 5.8% on the week; Detroit produced 111,000 st, down 3.5%; Lake Erie output was 42,000 st, up 2.4%; the Northeast Coast increased to 128,000 st, up 9.4%; and steel output in the West increased 15% to 91,000 st from 79,000 st a week earlier.

AISI's data is based on estimated raw steel production from a sampling of mills representing about 50% of total US steelmaking capacity.