TEHRAN — The head of Iran’s Revolutionary Guard has accused the United States, Britain and Pakistan, as well as Israel, of planning a suicide attack that killed 42.

The attack Sunday in south Iran killed five senior Revolutionary Guards commanders and 37 others. The attack occurred at a reconciliation meeting between Shiite and Sunni tribal leaders who gathered in southeastern Iran near the Pakistani border. The bomber was reportedly disguised in tribal dress.

“The American and Israeli intelligence agencies are behind this. We must pay them back in order to punish them, and, God willing, we hope to be able to do so,” Gen. Mohammad Ali Jafari said Monday.

The Muslim militant group Jundallah, or Soldiers of God, which operates along the Iranian-Pakistani border and is said to be affiliated with Al Qaeda, claimed responsibility for the attack, according to reports.

In related developments, Iran said it will further enrich uranium itself if nuclear talks in Vienna this week with the UN watchdog International Atomic Energy Agency, Russia, France and the United States in Vienna fail.

“If the talks do not bring about Iran’s desired result… we will start to further enrich uranium ourselves,” Ali Shirzadian, spokesman for Iran’s Atomic Energy Organization, told Iran’s official IRNA news agency a few hours before the talks were scheduled to start.

The meeting was to discuss details of sending Iran’s low-enriched uranium abroad for further processing and return to Tehran. The issue was agreed “in principle” between Iran and world powers in Geneva on Oct. 1. But Iranian authorities have so far shown no public hints of flexibility over Iran’s nuclear row with the West.

The UN Security Council has imposed three rounds of sanctions on Iran for refusing to stop its sensitive enrichment work.

Shirzadian said Iran had no intention of suspending its enrichment.

“Buying nuclear fuel from abroad does not mean Iran will stop its uranium-enrichment activities inside the country,” Shirzadian said.

The West fears Iran’s nuclear program is a front to obtain a bomb. Iran says it needs nuclear technology to generate power.

International negotiators are holding key talks with Iran that could see it handing over most of its enriched uranium for processing abroad.

Iran would not have enough material for a nuclear weapon if it exported most of its enriched uranium. Western nations suspect Tehran of seeking to build a weapon, but Iran denies that.

Monday’s talks followed a meeting between six world powers and Iran earlier this month. The West says that Iran agreed to transfer the uranium to Russia and have it turned into fuel for a small research reactor.

With files from Ha’aretz