WASHINGTON (AP) — The Food and Drug Administration announced a new proposal Thursday to try and head off more shortages of crucial medications that have disrupted care at hospitals and clinics nationwide.

Under the proposed rule, companies that make medically important prescription medicines would have to notify the FDA six months ahead of any changes that could disrupt the U.S. supply. That includes plans to discontinue a product or manufacturing changes that could slow production.

"The FDA continues to take all steps it can within its authority, but the FDA alone cannot solve shortages. Success depends upon a commitment from all stakeholders," said FDA's top drug regulator Dr. Janet Woodcock, in a statement.

FDA leaders say advance warnings help the agency work with companies to resolve supply problems or find alternate producers for drugs that are being phased out. The FDA credits earlier warnings from companies with reducing the number of drug shortages from 251 in 2011 to 117 last year.

Drug shortages in the U.S. have spiked over the past six years, particularly those involving inexpensive generic injected drugs, including powerful antibiotics, painkillers and anesthetics used in surgery. They are the workhorses of hospitals but are difficult to make and produce little profit for drugmakers.

Some cancer drugs also have been in short supply, disrupting treatments that require medication administered on a precise schedule.

The FDA proposal expands and strengthens existing requirements passed by Congress last year and an executive order issued by President Obama in 2011. Those measures require drugmakers who are the sole manufacturer of a drug to contact the agency ahead of any supply disruptions. Thursday's proposal would expand the requirement to any company making a drug that is "life supporting, life sustaining" or used to treat a "debilitating disease or condition." The FDA plan would also expand the requirement to non-drug biologic products, such as vaccines.

Penalties against companies that don't comply would not be very severe. FDA officials said Thursday the agency will post on its website "non-compliance" letters to companies that fail to provide enough advance notice.

"We think that putting those up would emphasize the importance the FDA is placing on timely notification," FDA deputy director for regulatory programs, Dr. Douglas Throckmorton, told reporters.

The FDA will take comments on its proposed rule for 60 days, before revising and finalizing it.

The forces behind recent drug shortages include consolidation among generic drug manufacturers, as well as manufacturers deciding to end production of marginally profitable drugs. Many shortages are also caused by problems with sterility and other serious issues that have led to shutdowns of production lines and occasionally entire factories. Recalls of huge batches of some drugs due to contamination by bacteria, fungi and tiny glass or metal particles have exacerbated shortages.

The recent spate of recalls has forced the FDA to increasingly allow imports from foreign factories that normally don't ship to the U.S.

While once considered an extraordinary step, the agency has been forced to allow the importation of 17 drugs to combat U.S. shortages. Most recently, the agency authorized temporary shipments from Norway of intravenous formula used to feed newborn infants, cancer patients and other frail patients who cannot eat or drink by mouth.