Jackson, Wyo. ? Federal Reserve Chairman Alan Greenspan said Friday the country would face “abrupt and painful” choices unless Congress acted quickly to trim Social Security and Medicare benefits for the baby boom generation. He said the government has promised more than it can deliver.

Returning to a politically explosive issue just before the Republican National Convention, Greenspan said the country must face up to “some tough policy choices.”

Government resources even under the most optimistic economic assumptions on growth and productivity will be inadequate to provide baby boomers with the level of benefits their parents got, he said.

Speaking at a two-day conference sponsored by the Kansas City Federal Reserve on challenges posed by an aging population, Greenspan said policy-makers must address the looming crisis in Social Security and Medicare before the first wave of 77 million U.S. baby boomers begin retiring later this decade.

“We owe it to our retirees to promise only the benefits that can be delivered,” he said. “If we have promised more than our economy has the ability to deliver … as I fear we may have, we must recalibrate our public programs so that pending retirees have time to adjust through other channels.”

And he warned, “If we delay, the adjustments could be abrupt and painful.”