The burgeoning relationship between Israel and Azerbaijan is raising eyebrows throughout the Middle East, not least of all because Azerbaijan is Iran’s neighbor to the north and shares close cultural and demographic ties with Iran.

Trade between Israel and Azerbaijan now totals $4 billion annually, the highest figure for Israel’s business with any of the now-independent countries that were part of the former Soviet Union, and there’s a frequent exchange of officials – most recently Israeli Foreign Minister Avigdor Lieberman, who visited Azerbaijan’s capital, Baku, this week. “Our relationship is very intense,” Mr. Lieberman said.

Azerbaijan’s position between Iran and Russia has long made it a diplomatic “den of spies,” where various, often hostile, countries – including the United States, Iran, Russia, and Israel – could gather intelligence on one another.

But it’s the nature of Israel’s trade with Azerbaijan that’s drawn the most interest. In February, Azerbaijan agreed to pay state-run Israel Aerospace Industries $1.6 billion for a wide range of military products, including drones and anti-aircraft and anti-missile defense systems. That’s nearly a quarter of the money Azerbaijan’s government takes in each year, $7.8 billion. Azerbaijan also provides about 30 percent of Israel’s energy needs.

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“Baku has an important role in Israel’s regional aspirations,” said an Israeli diplomat who has worked on several trade deals that involved Azerbaijan. He couldn’t be named because he wasn’t authorized to discuss the subject with a reporter.

Speculation on how far the relationship goes is rampant. Israel, after all, has been threatening to take military action against Iran’s nuclear program. A recent report in Foreign Policy magazine alleged that, in addition to the commercial ties, Israel has acquired access to airfields in Azerbaijan’s north that might be used in any attack on Iran.

Azeri and Israeli officials have denied the story. In a recent news report on Israeli preparations for a possible strike on Iran broadcast by Israel’s Channel 2, unnamed Israeli officials said there were “better, more practical options” than airfields in Azerbaijan. The program didn’t elaborate on what those might be, however.

That hasn’t made Iranians any happier about the Azeri-Israeli alliance. Relations between Azerbaijan and Iran have worsened steadily, and earlier this year Iranian officials summoned Azerbaijan’s ambassador to Tehran to the Foreign Ministry over reports that the Azeri government was allowing Israeli Mossad agents to gather intelligence along the Azerbaijan-Iran border.

In Azerbaijan, military analysts have speculated that access to Azeri airfields could be intended for drone missions over Iran, rather than a strike.

“There have been Western powers looking at the airfields in Azerbaijan for a long time and wanting to use them. Israel may have found a way,” said Arastun Orujlu, a former Azeri counterintelligence officer who’s the director of the East-West Research Center in Baku. He said it was well-known that Israel produced some parts for its drones in Azerbaijan and kept a large fleet outside Baku.

Azerbaijan has had Israeli drones since at least 2008, when they were first seen in a public parade. In September 2011, an Azeri drone of Israeli origin was shot down over Nagorno-Karabakh, a territory that’s the subject of a dispute between Azerbaijan and Armenia. That same month, the Azeri government announced that Israel’s Aeronautics Defense Systems had licensed it to build drones based on the Israeli model.

Under a deal struck this February, Azerbaijan is expected to acquire 60 Israeli-designed unmanned aerial vehicles.

Speaking to the Azeri news station News.Az, Azerbaijani political expert Rovshan Ibrahimov said Lieberman’s visit to Baku this week was the most recent in a long line of moves by Israel to threaten Iran through Azerbaijan.

“The arrival of Lieberman is part of the situation escalated around Iran by Israel. Here are some aspects of the fact that Israel is trying to show Tehran that it can at any time strike Iran, and for this makes certain steps to ensure the support of its allies in this plan,” he said.

Lieberman denied that his trip was meant to intimidate. He said his meetings with top officials in Baku, including President Ilham Aliyev, focused on bilateral relations, although his office released a statement that said Iran also had been on the agenda.