June 10 (Reuters) - The Obama administration and congressional Democrats are moving to tighten U.S. financial regulation to prevent another banking and market crisis.

Changes will affect banks, hedge funds, exchanges and other segments of the financial services industry. The administration is expected to unveil a comprehensive reforms package on June 17, covering some of the major issues listed below. Firms whose business models could be at risk under various proposed changes are listed in each section under "political risk exposure":

BANK REGULATION:

The Obama administration has been eyeing a plan to create a single government agency to regulate all banks.

But that approach may be losing traction in the face of the politically difficult task of consolidating four existing federal banking regulators.

Some lawmakers see the possibility of merging the Office of Thrift Supervision with the Office of the Comptroller of the Currency. Both are Treasury Department units.

Another option is moving some of the Federal Reserve's and the Federal Deposit Insurance Corp's bank supervision duties into the newly merged entity.

OTC DERIVATIVES:

The administration has proposed cracking down on over-the-counter derivatives with a plan to move more trading onto exchanges or into clearinghouses, supervise dealers more closely, and make this opaque market more transparent.