Bank of America could end up cutting 30,000 jobs as it moves to absorb Merrill Lynch, three times as many as previously estimated, sources told CNBC.

As of yesterday, sources were saying that layoffs could total at least 10,000 and would start before the end of the year.

But Bank of America CEO Kenneth Lewis wants to wring out $7 billion in savings from the merger over the next few years, so the total number of jobs lost could be closer to 30,000, they said.

Some of these job cuts could be through attrition or the sale of some businesses.

But the heaviest cuts will probably come in the investment banking business, which has dried up during the current credit crisis.