For years, U.S. employers have offered defined benefit, defined contribution or both types of pension plans to employees. However, one group is asking whether the nation needs an entirely new retirement system.

Led by the Schaumburg, Ill.-based Society of Actuaries, more than 50 pension leaders—including plan sponsors, academics, pension consultants and other professionals—have started a project called Retirement 20/20, and hope to create a new, more flexible retirement system.

Because the SOA has brought together so many different retirement plan stakeholders, it hopes that when the project is finished it will have widespread support.

In a recently released report, the group discussed the needs, risks and roles of current and future taxpayers, plan participants, markets and employers. The SOA also plans to hold a series of conferences to reach its goal of defining and promoting a comprehensive new pension system.

"We're trying to get a discussion started," said Emily Kessler, a fellow at the SOA. "All of these issues are understood in a fragmented fashion."

Ms. Kessler said a new type of retirement plan is needed because of society's changing needs. Employees increasingly have job and career changes, and retire at different ages with varying years of service. Employers' needs and market needs are changing as well, she said.

Because of the variables, the United States probably needs more than two main types of retirement plans, she said.

"We can't keep tweaking the system," Ms. Kessler said. "We want other options and more space in tax codes."

The group will research systems that can adjust to beneficiaries who work longer or live longer, for example, and how to get financial markets to work more efficiently for retirement plans.

In September the SOA will hold a conference to focus on aligning roles with the skills of plan participants, employers and money managers. It also will address tensions between taxpayers and retirement participants, Ms. Kessler said.

No time frame has been set for the final recommendations, she added.