BEIRUT (AP) — Iran's new president expressed his country's support to Syria's embattled leader Bashar Assad's regime Sunday, saying no force in the world will be able to shake their decades-old alliance.

Hasan Rouhani's comments came as Syrian troops and rebels fought some of the fiercest battles in the mountains of the coastal province of Latakia, an Assad stronghold.

Rouhani made the comments during a meeting in the Iranian capital of Tehran on Sunday with Syrian Prime Minister Wael al-Halqi, Syria's state news agency SANA said.

Syria has been Tehran's strongest ally in the Arab world since Iran's 1979 Islamic Revolution.

Iran has been one of Assad's staunchest backers since Syria's crisis began. Tehran is believed to have supplied Assad's government with billions of dollars since the country's crisis began in March 2011. Iran-supported Hezbollah also has sent fighters into Syria to bolster an offensive by Assad forces.

"The Islamic Republic of Iran aims to strengthen its relations with Syria and will stand by it in facing all challenges," SANA quoted Rouhani as saying in a report from Tehran. "The deep, strategic and historic relations between the people of Syria and Iran ... will not be shaken by any force in the world."

Rouhani was elected in June and was endorsed by the country's supreme leader on Saturday, allowing him to begin acting as president. He was sworn in Sunday.

Assad vowed Sunday evening to crush the rebels trying to overthrow him, saying Syria is between two choices: "a state of the law or a state run by thieves and bandits."

Assad spoke while taking part in an iftar, the meal that breaks the dawn-to-dusk fast during the Muslim holy month of Ramadan. The iftar was attended by government officials, religious leaders and members of the country's unions and political parties, SANA said.

It was Assad's second public appearance this week after he visited troops in the Damascus suburb of Daraya on Thursday to mark Army Day.

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Assad said "terrorism cannot be dealt with politically but should be struck with an iron fist."

Assad's troops have achieved victories in the past two months mostly near the capital Damascus and in the strategic central province of Homs that links the capital Damascus with Assad's stongholds on the coast.

Assad said his army, which was built to fight a conventional war against its main enemy Israel, has been able to adapt to the guerrilla warfare it is facing.

The Syrian leader criticized Persian Gulf states that he said are demanding democracy in Syria despite human rights abuses in their own countries.

"Their political systems belong to the middle ages where there are no parliaments or elections," Assad said.

Saudi Arabia and Qatar that have been among the strongest backers of the Syrian opposition.

Rouhani condemned foreign intervention in Syria, saying that the Arab country is passing through a "failed attempt" to strike at the "axis of resistance and rejection to Zionist-American plans in the region," SANA quoted him as saying.

Damascus and Tehran reject the idea that there is an uprising in Syria and say the country is being subjected to an Israeli-American conspiracy because of its support to militant groups such as Lebanon's Hezbollah.

SANA quoted Rouhani as saying that Syria will come out of this war "victorious."

Al-Halqi said the Syrian people will "not forget friends who stood by their side during times of difficulties," SANA reported.

More than 100,000 people have been killed since the uprising against the Assad family's four-decade rule began in March 2011. The revolt later escalated into a civil war, which has uprooted millions of people from their homes.

Assad's and Rouhani's statements came as Syrian troops and rebels fought Sunday some of the fiercest battles in the mountains of the coastal province of Latakia, an Assad stronghold.

The Britain-based Syrian Observatory for Human Rights said the clashes in the Jabal al-Akrad region in Latakia province began around dawn when rebels attacked government forces' posts. It said both sides used tanks, artilleries and mortars in the fighting, while government warplanes took part in the battles.

Although much of Latakia has been under the firm control of Assad's forces, some mountainous regions such as Jabal al-Akrad and Jabal al-Turkomen have witnessed fighting because they are close to rebel-held areas.

The observatory said 12 rebels, including foreign fighters, were killed in the fighting, as well as 19 troops and pro-government gunmen. Dozens were wounded as well, it said.

The Local Coordination Committees, another activist group, said at least eight people were killed in the fighting in Latakia province. It added that rebels fired Russian-made Grad rockets at government positions.