By Michelle Nichols

UNITED NATIONS (Reuters) - The United States pushed the United Nations Security Council on Thursday to focus on "illegal and dangerous behavior" by Iran and Lebanese group Hezbollah in the Middle East, an accusation that Iran dismissed as "misleading propaganda."

U.S. Ambassador to the United Nations Nikki Haley told the 15-member council that its monthly meetings on the Middle East - traditionally focused on Israel and the Palestinians, Syria and Lebanon - regularly turned into "Israel-bashing sessions."

"Iran is using Hezbollah to advance its regional aspirations. They are working together to expand extremist ideologies in the Middle East," she said. "That is a threat that should be dominating our discussion at the Security Council."

U.S. Secretary of State Rex Tillerson on Wednesday accused Iran of "alarming ongoing provocations" to destabilize countries in the Middle East as the Trump administration launched a review of its policy toward Tehran, including a 2015 nuclear deal.

"Today we heard unsubstantiated allegations against my country which I categorically reject as misleading propaganda campaigning against Iran and its role in the region," Iran's U.N. Ambassador Gholamali Khoshroo told the council on Thursday.

The United States, which is president of the council for April, tried to focus the meeting on Thursday on Iran, which it accuses of aiding Hezbollah in Syria, deadly militia in Iraq and Houthi rebels in Yemen.

In a note ahead of the meeting, the United States asked countries to consider: "Who are the regional players that most benefit from chaos in the region, and what are the connections between terrorist groups and these states?"

Several council members broadened their statements during the meeting on Thursday to discuss other conflicts in the Middle East, but few mentioned Iran.

Haley told the council: "The incredibly destructive nature of Iranian and Hezbollah activities throughout the Middle East demands much more of our attention. It should become this council's priority in the region."

Haley, who became the U.S. ambassador in late January, is a member of the Cabinet of President Donald Trump, who took a hard line on Iran during his campaign for the White House.

(Reporting by Michelle Nichols; Editing by Jonathan Oatis)