“It was a step in the right direction, but not enough of a step,” said Charles J. Ogletree Jr., a Harvard professor and a death penalty opponent who met with administration officials as part of the review. The Justice Department, he added, has been refusing to say what he thinks senior officials there believe: “We’ve had too many executions that didn’t work and killing somebody’s not the answer.”

In remarks last May after a prisoner in Oklahoma regained consciousness and writhed and moaned during a lethal injection, Mr. Obama, who has supported the death penalty, seemed to raise expectations for a policy change. He lamented its racial disparities and the risk of executing innocent people. He referred the matter to Mr. Holder, a liberal stalwart who opposed capital punishment. But privately the White House was cautious, sending word to the Justice Department to keep its focus narrow, administration officials said.

Mr. Obama called for the review at a time when there had not been a federal execution since 2003, when Louis Jones Jr. was killed for raping and murdering a 19-year-old female soldier. Since 2010, the federal government has effectively had a moratorium on executions — all are carried out by lethal injection — because manufacturers in Europe and the United States refused to sell the government the barbiturates used to render prisoners unconscious. States, however, found alternatives, including the sedative midazolam, which was used in the gruesome execution of Clayton D. Lockett in Oklahoma last year.

As the Justice Department sought advice from experts on both sides of the issue, opposition to the idea came from unexpected corners. Some of the most outspoken voices against the death penalty also urged the most caution, fearful that a federal announcement would actually do more harm than good.

Image Midazolam was used in the execution of Clayton D. Lockett in Oklahoma last year. Credit... Oklahoma Department of Corrections

“From my view, we’re better off with things bubbling up in the states,” said Henderson Hill, the executive director of the Eighth Amendment Project and one of several people consulted by the administration last year. “I’ve never been all that enthusiastic about the executive branch’s role.” While 32 states allow the death penalty, many have their own moratoriums on executions and the number of people put to death is declining.