Palestinian officials, viewing the current US administration as having a pro-Israel bias, declined to attend the conference.
Prime Minister Benjamin Netanyahu said on Tuesday that Israeli forces had carried out another strike in Iran-aligned Syria, a day after the Syrian army said an Israeli drone fired missiles near a demolished hospital and an army observation post.
"I have to tell you that the courageous decision of Sultan Qaboos to invite me to Oman is changing the world", Netanyahu said, referring to his October 2018 visit to Muscat.
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".
Arab nations and Israel faced a common threat of Iranian regional aggression and Washington was working closely with these nations to counter this, he said. It will also include discussion on the growing influence of Iran in the region.
Foreign ministers and other officials from more than 60 countries were gathering for the conference in Warsaw, which was starting on Wednesday evening and whose agenda included Iran, conflicts in Syria, Yemen and Israeli-Palestinian peace.
Prime Minister Benjamin Netanyahu raised eyebrows on Wednesday when he ostensibly called for "war with Iran".
A USA -sponsored Middle East conference aimed at building a coalition against what Washington sees as the threat posed by Iran also produced signs of a warming of ties between Israel and some Arab countries on Wednesday. Israel and Oman have unofficial economic relations but not formal diplomatic relations.
Netanyahu was hardly the only sanguine party. "Now we say, this is a new era, for the future".
The opening ceremony for the two day conference gets under way in Warsaw.
Noting that "a war with Iran is fundamentally at odds with the security interests of the United States, Israel, the people of Iran, and the entire Middle East", the group declared: "Whether the prime minister's words were intentionally muddled or not, his provocative message needs no interpretation". The Jerusalem Post reports that the Trump administration is unlikely to make a big splash at the conference with an announcement of its impending Israeli-Palestinian peace plan.