BOSTON -- A plan for replacing Massachusetts’ failed health insurance marketplace website will cost more than $120 million, state officials estimated Thursday, adding they hoped most of the money would come from the federal government.

The board overseeing the state’s health marketplace voted 10-1 to support a dual-track approach that calls for purchasing software that powers other states’ marketplace websites, while simultaneously laying the groundwork for a temporary switchover to the federal government’s health care marketplace, if necessary.

The plan follows the disastrous rollout of a state website that dramatically slowed the transition from Massachusetts’ first-in-the-nation universal health care program to the requirements of the federal Affordable Care Act.

Rebuilding the website was ruled out as an option, officials said, because it would be too expensive without guaranteeing a functional marketplace in time for the start of the next open enrollment period Nov. 15.

"It’s not as though we had other viable options," said Sarah Iselin, a health care executive hired by Gov. Deval Patrick to oversee a fix to the website woes, following the board’s vote.

Despite the problems, Iselin said the state has extended coverage to an additional 270,000 people and continues to lead the nation in percentage of residents insured. But nearly 160,000 people have been placed in temporary Medicaid coverage because the state has not been able to determine their eligibility for ACA-compliant plans.

"Simply starting over and building a website from scratch is not something we have either the time or money to do," Patrick told reporters Wednesday.

The state planned to ask the federal Centers for Medicare and Medicaid Services for additional funding to cover the estimated $121 million cost of the dual-track approach. The price tag includes about $56 million to purchase software from Virginia-based hCentive and $13 million to facilitate a switchover to the federal marketplace should the new program not be operational by the fall.

A group representing insurers expressed "serious concerns" that the two-pronged approach could lead to potential disruptions for consumers.

"We cannot overstate the complexity and technical issues that come with having to develop two separate systems," said Eric Linzer, senior vice president of the Massachusetts Association of Health Plans.

"The combination of the technical requirements, compressed timeframe and significant additional costs of having to build two systems may result in some health plans being unable to participate," the letter warned.

Amy Whitcomb Slemmer, head of the advocacy group Health Care for All, applauded the state’s strategy.

"Consumers expect a website and eligibility system that is easy to use and that allows them a choice of affordable plans that meet Massachusetts standards for good coverage," Slemmer said in a statement.