TheStreet.com Ratings lowered its financial strength rating on BankUnited Financial ( BKUNA) to E- (very weak), in response to the company's warning in a regulatory filing that it could be shut down by regulators. BankUnited said in a Securities and Exchange Commission filing Tuesday that the company had not been able to comply with a regulatory order to raise capital, and faced "enforcement action," which could include placing the bank into receivership." The company also said it didn't expect to file its annual 10-K report for its fiscal year ended Sept. 30, 2008 until the end of February. In the filing, the Coral Gables, Florida, holding company also increased its estimate of its net loss for the quarter ended Sept. 30 to $607 million, from a previous estimate of $327 million. The company said that when it made the previous estimate, its allowance for loan and lease losses "analysis was not yet completed." TheStreet.com Ratings had downgraded BankUnited to D- (weak), based on the original Sept. 30 Thrift Financial Report. The E- rating will be published soon on the Banks and Thrifts Screener. BankUnited had approximately $14.5 billion in total assets as of Sept. 30. It said that, based on the revised "preliminary loss" for the quarter, main subsidiary BankUnited FSB's tier-1 and risk-based capital ratios were 3.4% and 7.1% as of Sept. 30. The company didn't provide a revised leverage ratio. In order to be considered well-capitalized under regulatory guidelines, a bank or thrift needs to maintain leverage, tier-1 and risk-based capital ratios of at least 5%, 6% and 10%. BankUnited's revised figures for Sept. 30 would leave it undercapitalized according to the guidelines.