Liquefied natural gas shipments from Yemen, scheduled to pass through Boston Harbor on the way to Everett, have unnerved elected officials, who acknowledged Tuesday they are largely powerless to stop federal ratification of the deliveries.

U.S. Coast Guard Captain John Healey told state officials Tuesday that Yemeni LNG shipments into Boston Harbor, which the Coast Guard announced Tuesday would be permitted, "will be as safe as all the other shipments that come into the port.”

House Speaker Robert DeLeo and Boston Mayor Thomas Menino said they still had concerns about the plan, which drew new scrutiny after revelations that the attempted Christmas Day bomber trained in Yemen.

Healey said that each ship from Yemen would be evaluated individually, beginning with the first arrival, expected late this month. Up to 30 shipments are expected annually.

Healey said that LNG shipments worldwide, totaling 56,000 historically, have never resulted in a major explosion.

After a meeting at the State House, DeLeo said he would call the Coast Guard directly if he wanted to take more action to block the shipments.

“Any time you have anything of this sort coming through, in my case, my particular district, of course you have reservations,” said DeLeo. “But with those reservations, there has to be a balancing act, the providing of natural gas to the area, while at the same time the safety concerns that we have.”

DeLeo added, “Can I say today definitively today that everything’ OK and let’s move forward? No. I still want to go out and make sure that every possible safety method has been used.”

Public Safety Committee House chair Michael Costello said, "No one's ever going to be 100 percent comfortable" with the LNG shipments into the harbor.

Menino said in an emailed statement, “I am disappointed by the decision of the United States Coast Guard to allow the shipment of LNG from Yemen and believe that this is the wrong decision for the people of Boston and the metropolitan area.

“It is unreasonable and unsafe to continually put the interests of large corporations ahead of the security of Boston area residents and it is time to solve this problem once and for all,” Menino said. “Extra security alone is not a proper solution and it is the duty of the Department of Homeland Security, Department of Energy and the Federal Energy Regulatory Commission, to develop a long-term strategy that will significantly limit, if not eliminate, the need for LNG tankers to travel through Boston Harbor.”

Costello said developing offshore terminals, eyed as an alternative to land shipments, would be costly and long delayed.

Healey said the shipments had been under review for almost a year. Officials acknowledged that the attempted Christmas bombing, during which a Nigerian national trained in Yemen sought to detonate an airliner headed for Detroit, had fixed attention on the issue.

Healey said the Coast Guard could conduct additional and random checks of the ships as they pause outside the harbor.