In an excerpt of his book, "Decisions: My Life in Politics" published in the German weekly Der Spiegel on Saturday, Schroeder discusses the key political choices that marked his seven-year term in office, including his split with the US president over the Iraq war and the decision to call early elections.
"I am anything but anti-American," Schroeder told Der Spiegel in an interview to accompany the excerpt of the book which will go on sale on Thursday.
In the book, Schroeder, who led the Social Democrats to power in 1998, recalls that he had tears in his eyes as he watched television pictures of people jumping from the burning World Trade Centre on September 11, 2001.
He believed that Germany would have to react. He wrote: "It was important to me that Germany fulfill its requirements as an ally [of the US]".
"It was also fully clear to me that this could also mean the German army's participation in an American military mission," Schroeder wrote.
Several months later, during Bush's 2002 visit to Berlin, he was surprised at what he described as the US president's "exceptionally mild' speech to the German parliament.
"What bothered me, and in a certain way made me suspicious despite the relaxed atmosphere, was again and again in our discussions how much this president [Bush] described himself as 'God-fearing,"'
Gerhard Schroeder, former German Chancellor, in his memoirs 'Decisions: My Life in Politics'
While meetings with Bush at that time were friendly, Schroeder writes, he could not reconcile himself with the feeling that religion was the driving force behind many of the president's political decisions.
"What bothered me, and in a certain way made me suspicious despite the relaxed atmosphere, was again and again in our discussions how much this president described himself as 'God-fearing,"' Schroeder wrote, adding he was a firm believer in the separation of church and state.
Role of religion
"We rightly criticise that in most Islamic states, the role of religion for society and the character of the rule of law are not clearly separated," he added.
"But we fail to recognize that in the USA, the Christian fundamentalists and their interpretation of the Bible have similar tendencies".
Schroeder won a second term in office campaigning against joining the US in Iraq in 2003, but called early elections last year, after his Social Democrats suffered a series of setbacks at state level.
His party narrowly lost the election to the Christian Democrats, and although it remains in power as part of a left-right coalition, Schroeder lost the chancellorship to Angela Merkel and stepped down as party leader.