U.S. President Barack Obama’s actions to reduce nuclear weapons threats have not been commensurate with his rhetoric, an Australian professor says.

"Prevention, Pre-emption and the Nuclear Option: From Bush to Obama," by RMIT University’s Dr Aiden Warren, says Obama has struck bold rhetorical notes and promises to limit nuclear weapons.

But he said the president has stopped short of changing the status quo on critical issues that had lingered since the Cold War.

The lecturer from the School of Global Studies, Social Science and Planning at RMIT in Melbourne noted the U.S. continues to keep tactical nuclear weapons in its arsenal and keeps missiles on alert.

Warren said his book provided a comprehensive analysis of current U.S. nuclear weapons strategy.

“The book’s final section examines the extent to which Obama has attempted to ‘adjust’ the nuclear option with the recent release of the congressionally mandated Nuclear Posture Review,” he said.

The 254-page book, published by Routledge, encompasses Warren’s PhD thesis – as well an additional chapter – and offers new insights into what became known during the eight-year term of former President George W. Bush as the Bush Doctrine.