'Will never let you down', says Trump after clinching Republican nomination for US President

Donald Trump has officially clinched the Republican nomination for the US President after a state-by-state vote at the Party Convention.

"Such a great honor to be the Republican Nominee for President of the United States. I will work hard and never let you down! AMERICA FIRST!," Trump tweeted after the announcement.

After vanquishing 16 party rivals, warring with much of the Republican establishment and provoking controversy at the party convention, Trump secured the party's 2016 nominations for the White House.

He won majority of delegates - 1,237 - needed to contest the November 8 US Presidential elections.

Trump's campaign has been marked by frequent controversy over his rhetoric on Muslims, Hispanics, illegal immigration and trade, alarming many in the Republican establishment.

Party officials are hoping to use the four-day convention which began on Monday to smooth out some of his rough edges and present him as a job creator and a strong hand to combat security threats at home and abroad.

Republicans are also set to place in nomination Indiana Governor Mike Pence, Trump's choice for his vice-presidential running mate.