Republican vice-presidential candidate Sarah Palin has insisted she is ready to step in as US president if necessary.

In her first interview since becoming the vice presidential nominee for the Republicans, Alaskan Governor Sarah Palin has expressed confidence in her ability to fulfil the role of vice president and president if called upon, despite her lack of foreign affairs experience.

She told Charlie Gibson of ABC news she didn't hesitate to accept the offer of running mate from John McCain.