Moscow-- Russian President Vladimir Putin will host his Iranian counterpart on Friday to sign a broad agreement between Moscow and Tehran.

The Kremlin says the "comprehensive strategic partnership" agreement between Putin and Iranian President Masoud Pezeshkian will take their cooperation to a new level.

The signing comes ahead of the Jan. 20 inauguration of President-elect Donald Trump, who has pledged to mediate peace in Ukraine and take a tougher stance on Iran.

What to know about Russia-Iran relations:

Russia and Iran fought wars in the 18th and 19th centuries, with the Russian Empire occupying large tracts of territory in the Caucasus and Caspian Sea regions previously controlled by Persian rulers. In the early 20th century, Russian troops occupied much of northern Iran, but the Bolshevik Revolution of 1917 ended their presence. During World War II, the Soviet Union and Britain invaded Iran, which still brings back painful memories in Tehran.

Tensions were high during the Cold War when Tehran was an ally of the United States under the Shah of Iran. After his ouster in the 1979 Islamic Revolution, leader Ayatollah Ruhollah Khomeini denounced the United States as the "Great Satan" and the Soviet Union as the "Little Satan."

After the collapse of the Soviet Union in 1991, relations between Russia and Iran warmed. Moscow has become an important trading partner and a major supplier of weapons and high technology to Iran, which faces isolation from sweeping international sanctions.

Russia built Iran's first nuclear power plant in the port of Bushehr and put it into operation in 2013. The following year, Moscow signed a contract to build two more nuclear reactors.

Russia was part of a 2015 deal between Iran and six nuclear powers that provided Tehran with sanctions relief in exchange for curbing its nuclear program and accepting broader international scrutiny. Moscow provided political support to Iran when the United States unilaterally withdrew from the deal during Trump's first term.

After Syria's civil war broke out in 2011, Russia and Iran joined forces to support Bashar al-Assad's government against Turkish-backed rebels seeking to overthrow Assad. In 2015, Russia joined Iran and its proxies in launching a military campaign in Syria, helping Assad regain control of much of the country.

With Moscow focused on the fighting in Ukraine and Iran facing a challenge from Israel, they failed to prevent Assad's rapid collapse last month after a lightning-fast opposition offensive.

The West claims that after Putin sent troops to Ukraine in 2022, Russia and Iran signed a $1.7 billion Shahid drone agreement. The United States also believes that Iran has transferred short-range ballistic missiles, but neither Moscow nor Tehran has acknowledged these actions.

Iranian leaders have offered Putin strong political support, echoing his arguments to justify the conflict.

Tehran may want to secure Moscow's financial and defense commitments for its tattered economy amid the collapse of the 2015 nuclear deal and growing pressure in the Middle East.

Assad's fall is a major blow to Tehran's self-proclaimed "axis of resistance" in the region, following a punishing Israeli offensive against two Iran-backed militant groups - Hamas in Gaza and Hezbollah in Lebanon. . Israel has twice directly attacked Iran, with Israeli officials claiming the strikes destroyed Tehran's Russian-supplied S-300 air defense system.

Iran wants Russian long-range air defense systems and other weapons. It hopes to acquire Russia's advanced Su-35 fighter jets to upgrade its aging fleet, which has been embattled by sanctions, but Moscow has only offered a few Yak-130 trainers in 2023.

Trump’s “maximum pressure” policy on Iran heralds more trouble for Tehran. This month, he said the United States might conduct preemptive air strikes on Iran's nuclear facilities. Iran insists its nuclear program is for peaceful purposes, but some officials have increasingly suggested it may pursue nuclear weapons.

Kremlin spokesman Dmitry Peskov said the Comprehensive Strategic Partnership treaty covers everything from trade and military cooperation to science, education and culture. He denied any connection to Trump's inauguration, saying the signing was planned long ago.

Iranian Foreign Minister Abbas Araghchi described it as "a comprehensive treaty that takes into account all aspects of relations between the two countries, with the economic aspect being particularly important."

He told state television that while it covered defense and security cooperation, "it is a complete and comprehensive treaty rather than one focused on a specific purpose, such as a military alliance."

Despite official rhetoric, the two countries' tumultuous history has left many Iranians suspicious of Russia. The Kremlin's efforts to strike a balance between currying favor with Tehran and remaining friendly with Israel have added to the unease.

There are signs of growing dissatisfaction with Russia within Iran's powerful Revolutionary Guards, a paramilitary force that answers only to Supreme Leader Ayatollah Ali Khamenei. Last week, Iranian media leaked a recording of a security general blaming Russia for Iran's suffering in Syria.

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Associated Press writers Jon Gambrell in Dubai, United Arab Emirates, and Amir Wahdat in Tehran contributed.