USA-POLITICS/OBAMAA year and a half  into his presidency, Americans appear to be growing more uncertain about Barack Obama's religion.

A Pew Research Center survey shows that nearly one in five Americans -- 18 percent -- believe Obama is a Muslim, up from 11 percent in March 2009.  Meanwhile only about one third of Americans surveyed correctly describe Obama as a Christian, a sharp decrease from the 48 percent who said he was a Christian in 2009.

The survey was completed in early August, before Obama backed the controversial construction of a proposed mosque and Muslim cultural center near the site of the Sept. 11, 2001 attacks in New York.

Obama said last week he believed Muslims had the same right to practice their religion as anyone else in the country and supported their right to build the center in lower Manhattan -- comments that could add more confusion about his religion.

The Pew poll said the view that Obama is a Muslim is more widespread among political opponents than his supporters. In addition, beliefs about Obama's religion appear closely linked to his job approval rating.