Navy officials have committed to buying three of a new high-tech destroyer, about a month after telling Congress the service would buy only two of the ships, whose electronics are being built by Raytheon Co. workers in Rhode Island and elsewhere.

Navy Secretary Donald C. Winter and Adm. Gary Roughead, the chief of naval operations, announced their intentions in a letter to Rep. Patrick J. Kennedy, whose office made a copy of the letter public yesterday.

“We obviously are thrilled, absolutely thrilled by this news. This gives us an opportunity to fight another day,” Kennedy said in an interview yesterday.

Kennedy said he met with Roughead in Rhode Island and in Washington and met with Winter to push the case for the Zumwalt-class destroyers. “We had a lot of work to do to fight the Navy on this,” Kennedy said. “We put on a very strong, full-court press and had our facts straight.”

Also, he said, officials in the Defense Department and within the Navy were divided on whether to continue the Zumwalt program. “We were able to exploit that to our benefit.”

The Zumwalts, with stealth capabilities to enable them to prepare an approach for Marines landing on enemy shores, were planned as replacements for the Navy’s current destroyer, the Arleigh Burke class. Raytheon has about 2,000 employees, including nearly 500 in Rhode Island, working on the Zumwalt systems. Cancellation of the Zumwalt might not doom those jobs, though, because the technology could be used in other ships, such as retrofitted Arleigh Burkes and next generation cruisers and carriers. Raytheon’s equipment would run all computer systems on the ships, from launching missiles to sending e-mail.

Last month, Winter told Congress the Navy would halt production of the Zumwalt class, known as DDG 1000, after the two ships that are already under construction at Bath Iron Works in Maine and Ingalls shipyard in Mississippi.

But Roughead’s and Winter’s letter changed that.

“The Navy’s plan is to complete construction of the DDG 1000 ships currently under contract and conform to the President’s [fiscal year] 2009 budget submission by executing the third DDG 1000,” they wrote. “This plan will provide stability for the industrial base and continue the development of advanced surface ship technologies such as radar systems, stealth, magnetic and acoustic quieting, and automated damage control.”

The future of the Zumwalt class after next year “will of course be determined by the Department of Defense’s continuing assessment of existing and evolving threats, ensuring that it delivers those capabilities best suited to meet our national security needs both now and in the foreseeable future,” they wrote.

Those decisions will be made, though, after a new administration is in the White House.