US Secretary of State Mike Pompeo called for a "new era of cooperation" in solving the challenges of the Middle East, saying that no country could afford to stay on the sidelines.
"The United States is looking for a new era of cooperation among all our countries on how to address these issues," Pompeo told foreign ministers and other officials from more than 60 countries in Warsaw on Thursday.
He refrained from directly criticizing Iran, instead adding it to a list of regional challenges ranging from Syria and Yemen to Palestinian-Israeli peace.
"None of the challenges of the region will solve itself, we need to work together for security," he said. "No country can afford to stay on the edge."
Al Jazeera's Hashem Ahelbarra reported from Warsaw, saying that while many nations agreed that ending the wars in Syria and Yemen and the peace plan of Israel and Palestine were important, a number of questions regarding the effectiveness of the summit as Russia remained with China, the Palestinians and Houthis were not present.
Jared Kushner, son-in-law and Advisor to US President Donald Trump, attends the Warsaw conference, where he will speak behind closed doors about the contours of a US peace proposal to be presented after the April Israeli elections.
The Palestinian government does not participate, describing the conference as an "American conspiracy." It rejects US mediation after Trump recognized Jerusalem as the bitter capital of Israel in 2017.
The conference is widely regarded as a US-led effort to isolate Tehran, a Trump's foreign policy priority.
Iran was not invited to the meeting, despite being a "key player" in the region, Ahelbarra said.
"We are back in the first place, where it's all about Iran," he added.
Washington's European allies have expressed concern that the conference would turn into an Iranian meeting and increase tensions with Tehran. The top diplomats of the European Union stayed away.
Last year, the US withdrew unilaterally from the Iranian nuclear agreement and imposed sanctions on Tehran. However, European countries have continued to support the multilateral agreement as the best way to tackle the Iranian nuclear program.
At a meeting with Israeli Prime Minister Benjamin Netanyahu, Pompeo said Thursday that peace and stability in the Middle East could not be achieved without Iran.
Iran says its ballistic missile program is defensive and deterrent and that it has sent troops to Syria and Iraq only at the invitation of the governments of those countries.
Iranian Foreign Minister Mohammad Javad Zarif said at a press conference in Tehran on Wednesday that the two-day Warsaw meeting had been "dead on arrival".
The conference came on Wednesday when 20 members of the Iranian Revolutionary Guards were killed in a suicide attack in the southeast of the country.
Zarif described the meeting as the "Warsaw Circus" and said that it was "no coincidence that Iran was affected by terror on the day" when talks in the Polish capital began.
The Warsaw meeting brought together Israel and several Arab Gulf states, including Saudi Arabia.
The Israeli Prime Minister, who met with Oman's Foreign Minister on Wednesday, described the conference as a "historic turning point" in the fight against the Iranian threat.
"I think that this means a change, an important understanding of what threatens our future, what to do to secure it, and the opportunities for cooperation that extends beyond security into every aspect of the peoples of the Middle East Netanyahu, who is facing a vote on April 9, said.
Al Jazeera and news agencies