AT the very moment when the United States and European Union are pushing for a United Nations Security Council resolution to hem in Iran, their policies toward the Hamas-led Palestinian Authority are forcing Tehran and Ramallah closer together. That prospect is especially alarming under the current Iranian and Palestinian leadership.

In the past, sectarian and ethnic differences prevented the Palestinians and Iranians from forging an effective relationship. Today, though, the threats of President Mahmoud Ahmadinejad of Iran to eradicate Israel dovetail with the Hamas charter, which denies Israel’s right to exist. The closer Tehran draws to the Palestinian Authority, the likelier it is that the Iranians would retaliate against any American military action on their territory by encouraging Hamas to attack Israel. Arab countries allied to the United States would be happy to counter Iranian influence on Hamas, but they face significant obstacles.

Shortly after Hamas took power in March, the United States and European Union cut aid to the Palestinian Authority on the ground that it was now governed by a group that had been designated a terrorist organization. That left the authority unable to pay its 165,000 employees and helped produce a crisis in the West Bank and Gaza Strip.

Immediately, Hamas officials fanned out across the Arab world to drum up funds. Oil- and gas-rich Algeria, Qatar and Saudi Arabia committed money. The Arab League also promised financial support at its March meeting. But no funds were actually transferred to the Palestinian Authority, because the banks handling the contributions are wary of running afoul of American laws against financing terrorist organizations.

Iran, too, pledged to send money to the Palestinian Authority after a high-level meeting with two Hamas leaders in Syria. And the Iranian commitment is different from the Arab one. Although Mr. Ahmadinejad does not steer Iran’s foreign policy, his ideological rhetoric frames policy debates and could compel Iran’s Guardian Council to give Hamas much more money than Arab countries are willing to contribute.

Moreover, because Iran disregards American restrictions on financing terrorist groups, its money stands a good chance of actually reaching the Palestinian Authority, but for one impediment: no Iranian banks have offices in the Palestinian Authority, nor do any Palestinian banks have representation in Iran. This is a technical hurdle, easily overcome through the use of second- and third-tier off-shore banks that could handle Iranian funds destined for the Palestinian Authority.

On Tuesday, the United States endorsed a European proposal to establish a fund to channel aid to the West Bank and Gaza Strip. That fund will grant the Palestinian Authority a momentary reprieve. But by sidestepping the Hamas government and dealing only with President Mahmoud Abbas, the deal leaves the Palestinian prime minister and his cabinet hunting for money of their own.

The window to push Hamas to moderate its position is still open. If Arab governments are able to get their money to the Palestinian Authority, they stand a good chance of being able to compel Hamas to embrace the 2002 Arab peace initiative, abandon its charter and recognize Israel. But if Iran figures out how to get money to the Palestinian Authority before Arab countries do, Hamas will be in no position to say no, and Iran certainly won’t urge it to recognize Israel.

Geoff D. Porter is the acting director of the Eurasia Group’s division for the Middle East and Africa.