Saudi Arabia will formally confirm a $6 billion deal to acquire four "Multi-Mission Surface Combatants (MMSCs)" as part of an ongoing program to modernize and strengthen the Royal Saudi Navy.

The deal will be announced during the visit of U.S. president Donald Trump, who arrives in the kingdom on May 20 on a state visit.

The purchase of the four MMSCs, which are more heavily armed variants of the U.S. Navy's Freedom-class littoral combat ship (LCS), is the most important aspect of the of the Saudi Naval Expansion Program II (SNEP II).

The four warships are classified as frigates by the Royal Saudi Navy and will reinforce the navy's Eastern Fleet.

MMSC is described by its maker, Lockheed Martin, as a lethal and highly maneuverable multi-mission surface combatant capable of littoral and open ocean operation. It was designed from the keel up to confront modern maritime and economic security threats.

The MMSC takes the proven capabilities of the LCS and the flexibility of the Freedom-class hull to meet the unique maritime requirements of international navies. MMSC has a range of 5,000 nautical miles and can reach speeds in excess of 30 knots. It will utilize the same combined diesel and gas propulsion system as the LCS Freedom-class.

The frigate's main armament will be an 8-cell Mk-41 vertical launch system (VLS) and a 4D air search radar. They'll also be armed with eight RGM-84 Harpoon Block II anti-ship missiles (ASM); anti-submarine warfare (ASW) sonar suites and torpedoes.

Lockheed Martin claims the MMSC has the interoperability necessary for today's joint and allied naval force maneuvers. By deploying the MH-60R Seahawk, the MMSC will have a robust anti-submarine mission capability that is fully interoperable with the U.S. Navy and its coalition partners.

U.S. Department of Defense officials said sale of the MMCS to Saudi Arabia will enhance the stability and maritime security in the sea areas around the Arabian Peninsula and support strategic objectives of the United States.