JERUSALEM -- Israeli leaders told U.S. National Security Advisor Jake Sullivan on Thursday that Israel will continue its military offensive in the Palestinian enclave of Gaza Strip, despite the international calls for a ceasefire.

Sullivan was in Israel for meetings with officials as the United States voiced its concerns about the rising civilian casualties in the continued Israeli strikes on Gaza.

Speaking to the press alongside Sullivan, Israeli Defense Minister Yoav Gallant said that the war against Hamas "will require a long period -- it will last more than several months."

The two met in the Israeli Defense Ministry in Tel Aviv to discuss the Israeli offensive in Gaza, its border conflict with Lebanon, and dozens of hostages remain kept in Gaza, according to a statement released by the Israeli Defense Ministry.

Referring to the Yemeni Houthi forces' attacks on Israeli-linked ships as well as Eilat, an Israeli resort city on the shore of the Red Sea, Gallant said that Israel will support "international efforts in countering naval threats and will defend itself against any threat."

Later, Sullivan met with Israeli Prime Minister Benjamin Netanyahu, who thanked the U.S. for its "support for Israel in the supply of munitions, in blocking the attempts at the UN to stop the fighting, and in the assistance in returning our hostages."

Sullivan said that Israel has "the support of the United States as you take on this terrorist threat."