Bear Stearns, the U.S. investment bank battered by slumping mortgage markets, and China's CITIC Securities have agreed to swap stakes in each other and form a broad alliance, the firms said on Monday.

The deal would bolster access to business in booming China for Bear, which lags bigger Wall Street rivals in expanding its business beyond the United States, according to a CNBC website report.

Under the preliminary agreement, CITIC would invest about 1 billion U.S. dollars in Bear Stearns securities that would convert into about 6 percent of the New York-based investment bank.

Bear Stearns would buy 1 billion dollars of CITIC debt that would over time amount to a 2 percent stake in the Beijing-based firm. Neither company could hold more than 9.9 percent of the other's stock.