A terminal High Altitude Area Defense (THAAD) interceptor.
USA military sales to Saudi Arabia have come under increased scrutiny over the Saudi-led coalition's war in Yemen.
"We can speak only for ourselves", said Peskov.
The Saudi Arabian Ministry of Defense signed contracts for the S-400 air defence system, the Kornet-EM system, the TOS-1A, the AGS-30, and the Kalashnikov AK-103.
The THAAD - which has already been supplied to Saudi Arabia's neighbors Qatar and the United Arab Emirates - is one of the most capable defensive missile batteries in the USA arsenal and comes equipped with an advanced radar system.
The U.S.is also focused on increasing missile defense at home and for allies as tensions heat up in the Pacific and the Middle East, as well as with Russian Federation.
"This proposed sale will support the foreign policy and national security objectives of the United States by improving the security of a friendly country", the statement read.
DSCA noted that adopting THAAD weapons will help increase Saudi Arabia's capacity to defend against potential ballistic missiles and other regional threats.
"THAAD's exo-atmospheric, hit-to-kill capability will add an upper-tier to Saudi Arabia's layered missile defence architecture". "This visit is the beginning of strategic cooperation", al Harithi said.
Maria Vorobyova, an official at a Russian government agency dealing with military and technical cooperation, was cited earlier on Monday as saying that a firm agreement had been reached with Saudi Arabia on the S-400s.
Last week, Australia said it will outfit its new naval warships with Lockheed's Aegis air-defense system, which is also used by the USA and Japan and would help the three navies coordinate on missile-defense missions.
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