The deal depends on US approval, the senior Iraqi security officials told AFP, asking to remain anonymous because the matter is considered sensitive.

Tsurkov, a doctoral student at Princeton University, was kidnapped in Baghdad in March 2023.

There was no claim of responsibility for her abduction, but Israel accused Iraq's powerful Kataeb Hezbollah of holding Tsurkov.

The Iran-backed armed faction has implied it was not involved.

Iraq has been working to solve the issue which "depends on the Americans' approval for the release of the Iranian accused of killing an American citizen", a senior security source said.

The three Iraqi sources said that Washington has not yet agreed to this.

"The Americans have not yet agreed to one of the conditions, which is the release of the Iranian who is being held for killing an American citizen," one official said.

Iraq is both a significant ally of Iran and a strategic partner of the United States, and has for years negotiated a delicate balancing act between the two foes.

The Iranian and another four Iraqis were sentenced to life in prison in Iraq for murdering American civilian Stephen Troell, who was shot dead in Baghdad in November 2022.

In December last year, the US Justice Department announced that a "complaint was unsealed... charging" Iranian Mohammad Reza Nouri, "an officer" in the Islamic Revolutionary Guard Corps (IRGC), with allegedly orchestrating the killing.

Tsurkov, who is likely to have entered Iraq on her Russian passport, travelled to the country as part of her doctoral studies.

Security and diplomatic sources have told AFP they do not rule out the possibility that she may have been taken to Iran.

In November 2023, Iraqi channel Al Rabiaa TV aired the first hostage video of Tsurkov since her abduction.

AFP was unable to independently verify the footage or to determine whether she spoke freely in it or under coercion.