Salmond said a referendum was the "best route" to statehood, but added that there were others. He said if the Scottish parliament was given more powers until "you have a situation where you're independent in all but name... then presumably, you declare yourself to be independent", BBC reported.
"Many countries have proceeded through that route," he said in a TV interview.
He said if the main British parties failed to honour a pledge to devolve more powers to Edinburgh, then having another vote would be justified.
Salmond also said that demographics would see support for independence rising in the coming years.
"I mean when you have a situation where the majority of a country up to the age of 55 is already voting for independence then I think the writing's on the wall for Westminster," he said.
"I think the destination is pretty certain, we are only now debating the timescale and the method.
"I think Scots of my generation and above should really be looking at themselves in the mirror and wonder if we by majority, as a result of our decision, have actually impeded progress for the next generation which is something no generation should do," Salmond said.