Baghdad - Iraqi Sunni tribal sheikhs threatened to resort to the United States' rival in the region, the Islamic Republic of Iran, to get the needed military support in their fight against the Islamic State of Iraq and the Levant (ISIL), if the US did not respond to their demands, warned Iraqi lawmakers and tribal sheikhs.

The warning came during a meeting with US Senator, John McCain, who embarked on a short visit to Baghdad on Friday.

McCain met with several Iraqi lawmakers and tribal sheikhs representing the Sunni-dominated provinces of Anbar, Saladin, Diyala as well as the towns constituting the belt of Baghdad, to discuss proposed plans to confront ISIL.

Three Iraqi Sunni figures who attended the meeting told Al Jazeera that a list of demands was submitted to McCain asking for US ground troops, weapons and funds to accelerate the liberation of areas seized by ISIL and grant them (Sunni tribes) a bigger role in the battle against ISIL.

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The disgruntled tribal leaders, according to Sunni figures, made it clear that they were considering alternative options to get the much needed military support to drive away ISIL fighters, and that Iran was on top of the list of alternatives.

"[McCain] was told clearly that if the Americans kept watching the situation [in Anbar, Saladin and Diyala provinces] and did not intervene, we will ask another regional power to fill the gap," a senior Iraqi lawmaker who attended the meeting, told Al Jazeera on condition of anonymity.

"We have already opened many channels with Iran and they have offered unconditional support including weapons, funds and even fighters if required," he said.

The attendees have expressed their anger and dissatisfaction at the US and the [US-led] international coalition that does not support them in its war against Daesh [ISIL] while they rose up when Daesh got close to the Kurdish region and quickly, intervened. - Salah al-Joubori, senior Sunni lawmaker

ISIL fighters overran the second largest city in Iraq, Mosul, in June, with hardly any resistance from the Iraqi army. A few days later, ISIL fighters seized the neighbouring province of Salahuddin and vast parts of southern Kirkuk.

They now have control over most of the cities and towns of the Sunni-dominated province of Anbar.

Iran was the first regional country that responded to the Iraqi government's calls for assistance to stop ISIL advances towards the capital.

Iranian military commanders, accompanying Iraqi forces and Shia militias, have played a vital role in gaining control over the border towns of Jalawla and Saadia, in Diyala province, a few weeks ago and driving ISIL fighters from Jurf al-Sakhar, one of the main supply routes for ISIL in southern Baghdad.

Iran, according to analysts, was also quick to cover the large shortage of weapons and ammunition for the Iraqi troops and Kurdish forces.

On Sunday, official Iranian media reported that an Iranian Revolutionary Guards commander, who was training Iraqi troops and militia fighting ISIL, was killed in the Iraqi city of Samarra.

McCain, who was mostly just listening during the meeting, according to the lawmaker, asked for clarification relating to that point.

"McCain stopped us a lot when it came to that point, he looked very interested and was asking questions like who, when, where, why and how," the lawmaker said.

The meeting which lasted 90 minutes was held at the house of the Iraqi speaker, Saleem al-Joubori, in the Green Zone, the most fortified area in Baghdad that contains governmental buildings and many foreign embassies including the US and British embassies.

The tribal leaders and lawmakers had also expressed their dismay at the lack of a serious US policy to liberate their lands and "the US' double standards" in dealing with the Sunni tribes in these provinces compared to the Kurds.

"The attendees have expressed their anger and dissatisfaction at the US and the [US-led] international coalition that does not support them in their war against Daesh [ISIL] while they rose up when Daesh got close to the Kurdish region and quickly intervened," Salah al-Joubori, a senior Sunni lawmaker who also attended the meeting, told Al Jazeera.

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Salah al-Joubori, who confirmed that Sunni tribes have threatened to get assistance from Iran, added that McCain did not make any promises or offer any plans to explain how the US will address their demands although the meeting was "frank and realistic".

"The man is a senator and he has nothing to do with the decision-making [related to arming and funding the Sunni tribes]. He will transfer all what he heard, in addition to the written list of demands, to Congress," Joubori said.

US to help Iraq train and arm tribesmen as part of a future National Guard [EPA]

Iraqi Sunni leaders who met McCain, as several senior officials who are familiar with the talks confirmed, were hoping to convince the US administration to put pressure on the Iraqi government to form the long-awaited National Guard troops, arm the Sunni tribes and keep the Kurdish forces and Shia militias away from the Sunni areas.

"US is able to put great pressure on the Iraqi government and force it to form the National Guard, support the [Sunni] tribes and prevent the Peshmerga and Shia militias from entering the Sunni areas," a senior Sunni figure told Al Jazeera on condition of anonymity.

"We believe that the Iraqi government is deliberately holding up the formation of the National Guard and does not support the [Sunni] tribes."

In a briefing held on Saturday at the US embassy in Baghdad, McCain told reporters that the US will train and arm Sunni tribal fighters who will be part of the planned National Guard troops in Anbar.

"The Iraqi government will arm 4,000 tribesmen, in Anbar, within the National Guard troops which will be formed [later], and their training and arming will be through the Iraqi government," he said.