June 10 (Reuters) - U.S. offshore drilling contractor Noble Corp will acquire smaller rival Diamond Offshore Drilling in a $1.59 billion cash-and-stock deal, the companies said on Monday.

Noble will pay $15.52 per Diamond Offshore share, of which $5.65 will be in cash and the rest in Noble shares -- an offer that the boards of both companies have approved, they said.

The offer represents an 11.4% premium to the closing price of Diamond Offshore's stock on Friday.

Noble said it would fund the cash portion of the deal through a new secured $600 million committed bridge financing facility.

It expects the deal to immediately add to its free cash flow per share and estimates annual pre-tax cost synergies of $100 million, 75% of which it expects to come within one year of the deal closing.

Nobel's board also approved a 25% increase in its quarterly dividend to 50 cents per share. (Reporting by Gursimran Kaur in Bengaluru; Editing by Nivedita Bhattacharjee and Savio D'Souza)