Donald Trump's controversial wall along the US - Mexico border will be finished in 2 years, according to Homeland Security Secretary John Kelly.

Secretary Kelly said the wall should be finished in two years, photo: Reuters

'I really hope to have it done within the next two years,' Kelly told Fox News Channel in his first interview as DHS chief.

The retired four-star Marine general, who was sworn in on Inauguration Day, said he believed construction of the wall, one of Trump's most prominent campaign promises, would likely start in a few months.

The plan is to build the wall where it's needed first and then fill it in, Kelly believed.

'We have the authority to build it and we're looking at the money aspect,' he explained. 'I know that the White House is working with the Congress on discussions on when we might be able to press on with building it.'

'I think the funding will come relatively quickly and like I said, we will build it where it's needed first as identified by the men and women who work the border,' he added.

Man power, Kelly noted, is also an important component to securing the border.

'Any discussion about the protection of our southwest border involves discussion of physical barriers but also of technological sensors, things like that, but it's a layered approach and it's got to be backed up by great men and women who are going to make sure that the wall is intact.'

Asked about hostility from Mexican about the American plan to build a wall, Kelly remarked, 'I'd really like to establish a relationship on this, on the other side. It would be a mutually beneficial relationship.'/.