WBUR's Martha Bebinger reports:

The state's largest employer group says it may sue the federal government over a provision in Obamacare that will hike premiums for some small businesses.

The federal health care law changes the way individual and small business insurance rates are calculated.

The Obama administration agreed to let Massachusetts phase in the new system, but said in a letter today that the state must eventually comply.

Under the changes, some employers will see their rates drop, but others may see dramatic increases.