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WASHINGTON, June 3 (Reuters) - Al Qaeda's second-in-command Ayman al-Zawahri is expected to issue a new statement calling for an end to Israel's economic blockade of the Gaza Strip, U.S.-based Internet monitors said on Tuesday.

The statement was produced by al Qaeda's media arm, as-Sahab, and an announcement of its impending release was posted to Islamist Web forums, the SITE Intelligence Group said. Monitor IntelCenter said the audio-video release was expected within 72 hours.

Zawahri is following recent statements by Osama bin Laden that also reflected an increased emphasis by al Qaeda on the Palestinian issue. Analysts say al Qaeda is in a competition with Hezbollah for Islamist support.

The SITE Intelligence Group said bin Laden's top aide will address the upcoming anniversary of the June 1967 Six Day War after which Israel occupied the West Bank, including Arab East Jerusalem, Gaza, Sinai and Golan Heights.

Al Qaeda has vowed attacks on Jews both within and outside Israel. Despite calls by al Qaeda supporters for the militant network to establish a presence in Palestinian areas, U.S. intelligence officials see no evidence it has done so.

Bin Laden on May 18 urged Muslims to break the Israeli-led blockade of the Hamas-controlled Gaza Strip and fight Arab governments that deal with the Jewish state.

In his last message on April 22, Zawahri urged Muslims to back the self-styled Islamic State in Iraq, which he said posed the biggest threat to U.S.-led forces.

U.S. and Pakistani officials have said they believe bin Laden and Zawahri are hiding somewhere on the Afghanistan-Pakistan border. (Reporting by Randall Mikkelsen; Editing by Jackie Frank)

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