Iraqi Prime Minister Haider al-Abadi has rejected a proposal from Kurdish leaders to "freeze" the results of the secession vote, saying only a complete annulment would be a sufficient condition for the resumption of talks between Baghdad and Erbil.

Speaking to reporters in the Iranian capital Tehran on Thursday, al-Abadi said his government had warned Iraq's northern Kurdish region against holding the referendum - the results of which overwhelmingly supported Kurdish secession.

"As we told our brothers in Kurdistan in the past, we will not allow the danger of disintegration to put our country at risk," al-Abadi said.

"We will only accept the abolition of the referendum and the adherence to the Constitution," he added, describing military operations taking place on the outskirts of the region's borders as "constitutional" and aimed at "extending federal authority over those areas."

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On Wednesday, the Kurdish Regional Government (KRG) proposed to freeze the outcome of the referendum and open talks with Baghdad, while calling for an "immediate ceasefire and cessation of military operations" in the Kurdish region.

The KRG proposal came just days after Iraqi forces took control of the Kurdish-held Kirkuk, with the support of the Shia militia, the Popular Mobilisation Units.

Al-Abadi's trip to Iran on Thursday is seen as a continuing effort to bolster Baghdad's call for a unified Iraq.

After meeting with Iran's President Hassan Rouhani on his second visit to Tehran in four months, al-Abadi stressed the need for greater cooperation between the two countries.

"The strengthening of relations between Iraq and Iran is not only important for us - but for the whole region's security, stability and prosperity," he said.

Al-Abadi also met Iran's Supreme Leader Ayatollah Ali Khamenei.

In a statement from his office, the Supreme Leader said he "gave his support for measures taken by the Iraqi government to defend the unity, sovereignty and territorial integrity of Iraq".

Mahjoob Zweiri, Associate Professor of Contemporary History of the Middle East at Qatar University, said he expects more military cooperation between Iraq and Iran, following al-Abadi's visit.

"There [are] very strong bilateral relations between Baghdad and Tehran since 2003," Zweiri, an Iran expert, told Al Jazeera.

Zweiri cited Iran's role in Iraq's successful effort to defeat and drive out the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group from Mosul and other parts of Iraq.

The Tehran-backed Popular Mobilisation Unit fought alongside the Iraqi forces to combat ISIL. On Monday, during his meeting with US Secretary of State Rex Tillerson, al-Abadi rejected the US call for the Shia militia to leave Iraq, saying it is "part of the Iraqi institutions".

Zweiri also said that showing solidarity towards Baghdad on the Kurdish question also serves Tehran's interest in the region.

He said that an independent Iraqi Kurdish region, which is backed by Israel, "is not something Iran wants to see".

Saudi influence in Iraq

Seyed Mohammad Hashemi, a Tehran based journalist, told Al Jazeera that aside from the discussion on the Kurdish issue and the Kirkuk offensive, he expects al-Abadi to "carry a message on behalf of the US administration" about the Iran nuclear deal and the possibility of further negotiations.

In recent weeks, US President Donald Trump had announced that he would no longer certify that Tehran is in compliance with the nuclear deal, and called on allies to renegotiate the deal.

Hashemi also said that with the upcoming Shia Muslim holiday of Arbaeen, a time when many Iranian pilgrims travel to Iraq, he expects al-Abadi to discuss security measures and coordination. In the past, Shia religious events and holy sites in Iraq had been targeted with deadly suicide attacks and bombings.

Meanwhile, Hashemi dismissed speculations that Saudi Arabia may be drawing Iraq from Iran's geopolitical orbit, following al-Abadi's recent visits to Riyadh.

"I don't think Iran is very much concerned about Saudi Arabia's role in Iraq," he said.

"That is because the commonalities between Iranian and Iraqi people in social, cultural and religious spheres are great and already profound."

"We have heard Saudis want to play a role in Iraq's reconstruction," he added.

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"However, I don't think the Saudis, who have their own problems with their ambitious economic plan, will be able to fulfil pledges they made to Baghdad," Hashemi said.

Zweiri, a Doha-based scholar of Iranian politics, agreed with Hashemi's assessment on the Iraq-Saudi relations saying that "there's loads of obstacles and mistrusts" between the two countries.

"I don't think the normalisation between Baghdad and Riyadh will happen quickly," he said, adding that among the Iraqi political establishment, there is still many "who are not keen to develop relations with Saudi Arabia".

With additional reporting by Ted Regencia. Follow him on Twitter @tedregencia.