Around 80 countries are participating, including Israel.
The initial tweet, translated from Hebrew, had the prime minister saying: "What is important about this meeting, and it is not in secret, because there are many of those-is that this is an open meeting with representatives of leading Arab countries, that are sitting down together with Israel in order to advance the common interest of war with Iran".
Netanyahu expressed similar sentiments when he met earlier in the day with Omani Foreign Minister Yusuf bin Alawi bin Abdullah, telling him that the recent rapprochement between the two countries was "changing the world".
Washington initially touted the summit as a way to counter Iran's influence in the region, drawing condemnations from Tehran and leading several nations to send lower-ranking officials instead of their top representatives.
Netanyahu's surprising October 26, 2018, visit to Oman marked the first time an Israeli leader publicly visited the Gulf state since 1996.
Netanyahu - who has been trying to play up his diplomatic gains ahead of Israel's April election - has frequently hinted at warmer ties with Gulf Arab states.
Compare Mercedes' new W10 and last year's vehicle
Mercedes has already run its W10 on track today (Wednesday) at Silverstone for a shakedown that is being held behind closed doors. Ex-Force India racer Esteban Ocon will act as back-up to the pair after missing out on a 2019 race seat.
Vice President Mike Pence is leading the US delegation, accompanied by Secretary of State Mike Pompeo and White House advisor Jared Kushner. And how they always get made when we say this?
Several million Yemenis face starvation and the country has suffered one of the worst cholera outbreaks in modern times as Saudi Arabia and the United Arab Emirates - backed by the USA - seek to bomb and blockade the country's Houthi rebels into surrender.
"Iran isn't behaving like a normal country".
European Union policy chief Federica Mogherini, a key player in the Iran nuclear deal, will also not attend the two-day conference due to scheduling issues, an European Union official said, although Pompeo will travel to Brussels on Friday to meet with her.
Netanyahu and bin Alawi are now in Warsaw to attend a so-called "Ministerial to Promote a Future of Peace and Security in the Middle East", which is being co-organized by the United States and Poland. In a joint op-ed published Wednesday morning on CNN's website, Pompeo and Polish Foreign Minister Jacek Czaputowicz wrote that the summit will deal mainly with the civil wars in Syria and Yemen, as well as the Israeli-Palestinian conflict and other security-related regional matters.
Kushner, who is President Donald Trump's son-in-law, will brief delegates behind closed doors on Thursday on US plans for peace between Palestinians and Israelis.
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