Even though Senator Hillary Rodham Clinton raised $21 million in March, her campaign continues to struggle with a cash squeeze as her unpaid bills mount and she spends more money than she is taking in, according to new campaign finance filings.

Mrs. Clinton, of New York, currently has $10.3 million in outstanding primary debts but only $9.5 million available to cover them, leaving an $800,000 shortfall at the end of March. In February, the Clinton campaign had unpaid bills of $8.7 million and $11.7 million in cash.

By comparison, Senator Barack Obama of Illinois, who raised $42 million in March, had $43 million in cash for the coming primaries and a campaign debt of less than $660,000 at the end of March. Mr. Obama is spending 75 cents for every dollar he is taking in; Mrs. Clinton is spending $1.10.

In a conference call with reporters on Monday, the Clinton campaign sought to quell any concerns about finances. Howard Wolfson, a campaign spokesman, said, “This campaign has resources,” and added, “We will be honoring our debts in the coming months.”