Iran pledged strong support for Syrian President Bashar Assad on Tuesday, accusing the United States of "warmongering" and promising to back Assad's crackdown against rebels of the Syrian uprising.

According to the BBC, Iran's security chief Saeed Jalili said during a meeting with Assad that "Iran will not allow the axis of resistance, of which it considers Syria to be an essential part, to be broken in any way."

The meeting follows a weekend incident during which 48 Iranian religious pilgrims were kidnapped outside of Syria's capital city of Damascus. Iranian media reported on Monday that three of the pilgrims have been killed.

Iran's Deputy Foreign Minister Hossein Amir Abdollahian blamed the incident on Syrian rebels and United States intervention.

"Because of the U.S. manifest support of terrorist groups and the dispatch of weapons to Syria, the U.S. is responsible for the lives of the 48 Iranian pilgrims abducted in Damascus," he said, according to the Guardian.

Iran's promises to cooperate with the Syrian regime are nothing new. The two countries have long been allied to each other.

This has something to do with the fact that both are ruled by Shiite Muslims -- Iran is presided over by the Grand Ayatollah Ali Khamenei while the Syrian regime is mostly Alawite, a Shia sect. But the extent to which religion influences civilian life in both countries is markedly different, with Iran functioning as a theocratic state since 1979, and Syria -- which has a majority Sunni population -- remaining comparatively secular.

The countries' connection is, in fact, based more in strategy than on religious similarities. Both regimes have pooled their resources to resist Western and Israeli initiatives, support Islamist groups like Hezbollah and Hamas, and act as a bulwark against Sunni Arab dominance in the Middle East.

Iran has consistently sided with Assad since the Syrian uprising began in March of last year. Meanwhile, rebel forces, loosely organized to form the Free Syrian Army, have struggled against Assad's formidable army for the past 17 months. Over 20,000 people have died so far, according to the Syrian Observatory for Human Rights, and hundreds of thousands more have been displaced by violence.

Assad's grasp on power has lately been threatened by increased violence near government headquarters in Damascus, and by ongoing defections of high-profile dignitaries and military members.