GMAC LLC on Tuesday reported a first-quarter loss that was 15 percent larger than a year earlier. reflecting an increase in soured loans as the economy weakens.

The net loss increased to $675 million from $589 million a year earlier.

Profit from auto finance fell 13 percent to $225 million. Mortgage operations, including the Residential Capital LLC unit lost $125 million, the 10th straight quarterly loss, although that amount declined from $859 million a year earlier.

The effects of a soft economy and weaker credit performance on legacy assets continued to put pressure on GMAC's financial performance, Chief Executive Alvaro de Molina said in a statement.

GMAC is based in Detroit, and ResCap in Minneapolis.

GMAC reported results two days before the government is expected to release the outcome of its stress tests of 19 banks, including GMAC. Some analysts believe officials will direct GMAC to find more capital over the next six months.

(Reporting by Jonathan Stempel; Editing by Derek Caney)