ABC News' Jessica Yellin and Jonathan Karl Report: UN Ambassador John Bolton will end his service in the Bush administration when his appointment ends at the end of the 109th Congress. Bolton will not be seeking another appointment.
A White House spokesman says, "It's a decision that the President is reluctantly accepting."
Bolton's resignation is effective this weekend. Alex Wolff -- currently Bolton's deputy -- will serve as acting Ambassador until a successor is named.
The President will meet with Bolton and his wife Gretchen later this afternoon.