The American ambassador to Iraq, Zalmay Khalilzad, shook hands yesterday with a senior Iranian envoy and exchanged a few words in Farsi in what may have signified a slight warming of the frosty relations between the two nations.

The meeting with Abbas Arakji, the envoy from Tehran, came during a one-day conference aimed at curbing the violence in Iraq.

The talks, which were marred by an attack on the foreign ministry compound in Baghdad where they took place, presented a rare opportunity to bring the US and its old foes, Iran and Syria, to the negotiating table.

Washington has accused Tehran and Damascus of fuelling the war by providing weapons and support for Shi’ite militias and Sunni insurgents respectively.

The US and Iran have not had diplomatic ties for more than a quarter of a century since militants stormed the American embassy in Tehran.

Khalilzad called on Iraq’s neighbours to do more to help the country’s transition towards stability and prosperity. In a warning to Iran over its support for Shi’ite militias he said Iraq’s neighbours must take action “to halt the flow of fighters, weapons and other lethal support to militias and other illegal armed groups, and cease sectarian rhetoric and other propaganda that could incite violence”.

It was midway through the conference that two loud explosions from mortar fire shook the foreign ministry building, smashed windows and interrupted the delegates’ speeches.

Elsewhere in Baghdad a suicide bomb exploded at an Iraqi army checkpoint on the edge of Sadr city, in the northeast of the city, killing six soldiers and wounding 20 civilians.

The contacts between the US and Iran were essentially symbolic but may pave the way for more substantive talks next month in Turkey that Condoleezza Rice, the secretary of state, will attend.

Nouri al-Maliki, the Iraqi prime minister, appealed to his neighbours to cooperate to defeat terrorism and the insurgency.

He warned: “Iraq needs support in this battle that not only threatens Iraq, but will spill over to all countries in the region.”

Iranian media reports quoted the head of Tehran’s delegation as saying that Iran saw the summit as a “test” of whether the US was serious about trying to solve Iraq’s problems.

Tehran’s delegation called for the release of several Iranian nationals detained by American forces in Iraq, claiming they had diplomatic status. Khalilzad replied: “The coalition does not have anyone in detention who is a diplomat.” He added that the Americans would protect Iraq from “foreign elements who are contributing to violence”.

The conference also marked a breakthrough for Saudi Arabian diplomacy. The kingdom has been working behind the scenes to encourage contacts between the US and Iran. A German woman and her son, who were kidnapped in Iraq last month, will be killed in 10 days unless Germany withdraws its forces from Afghanistan, according to threats made in video footage shown yesterday.

The video, from a previously unknown group group calling itself the Arrows of Righteousness, showed Hannelore Krause, 61, sitting next to her son alongside masked gunmen. Germany has about 2,700 troops in Afghanistan serving with Nato.

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