Export sales in August rose to a record and the monthly trade deficit fell to its lowest level since January, the Commerce Department said yesterday. The report suggested a rosier outlook for third-quarter growth, but analysts warned that a weakening dollar could drag down domestic demand in the months ahead.

The gap between what Americans import and export shrank 2.4 percent in August, to nearly $57.6 billion, an improvement over analysts’ expectations. The July deficit was revised lower, to $59 billion, a drop of about $250 million, the department said.

A weakening dollar, which reduces the monetary value of exports, had the counterbalancing effect of contributing to the increase in exports — good news for American producers. Export sales rose 0.4 percent, to $138.3 billion, in August, led by strong business in food and industrial supplies. Total export sales have risen 12.8 percent since August 2006.

Imports fell 0.4 percent, to $195.9 billion, as pharmaceutical and automotive imports dropped. But Americans purchased more foreign clothing and technology products, like semiconductors.