WASHINGTON — The Obama administration is ending a problem-plagued program to train and equip Syrian rebels to fight the Islamic State, saying it will use the hundreds of millions of dollars from Congress to help Kurdish fighters and other groups that have had some success reclaiming territory from the militants.

The strategic shift represented an admission by the Pentagon and the White House that the $500 million training program, which President Barack Obama heralded less than a year ago as a centerpiece of the United States’ campaign against the Islamic State, had failed.

“Clearly we have had significant challenges associated with our training-and-equip program related to our counter-ISIL mission, and we have been looking at ways to address those deficiencies,” deputy national security adviser Ben Rhodes said, using a common acronym for the Islamic State.

“At the same time, we have seen opportunities emerge where we’ve been able to equip forces fighting ISIL on the ground in Syria and seen them make significant gains, particularly in northeastern Syria,” Rhodes said. “So today’s announcement represents an ongoing process where we aim to learn from what works in our strategy and aim to make corrections where we see things that are not working.”

Pentagon chief Ash Carter said he had been unhappy with the results of the effort to train Syrians in Turkey and then dispatch them back to their homeland to fight the Islamic State.