The Obama administration says its new plan to help troubled homeowners won't stop all foreclosures but could help as many as 4 million.

The effort is designed to help two groups.

The first are borrowers who owe more on their loans than their houses are worth. According to Moody's Analytics, nearly 15 million homeowners fall into this category. Mortgage companies would receive incentive payments from the government to cut the total amount the borrower owes. Or, the homeowner can refinance into loans backed by the Federal Housing Administration.

The second group is unemployed borrowers. Homeowners collecting unemployment would see their mortgage payments cut to no more than 31 percent of their monthly income for up to six months.

The administration is also specifying the people it's not going to help. Those groups include investors, speculators, people living in "million dollar homes," and those who default on vacation homes.