The U.S. market for mortgage-backed securities is increasingly on edge this week as a dour economic outlook fans speculation that the government will come to the aid of homeowners who have been unable to take advantage of record low interest rates. Traders reported the most volatile trading this year in some MBS amid speculation that the Obama administration would remove at least some hurdles to refinancing for borrowers with weaker credit and whose loans are underwater. The administration has been weighing numerous options to stabilize the battered housing market–a key source of weakness in the economy. Administration officials have been studying ways to increase the number of homeowners who can refinance, but haven’t settled on a definite plan.