At a conference in Dahuk in the Kurdistan Region of Iraq a few weeks ago, I was intrigued to see the leader of the Kurdish Democratic Party of Iran (KDP-I) -- which the Tehran regime considers a subversive, terrorist group -- address the assembled notables. Sitting in the front row were three of the most senior political and security officials of the Kurdistan Regional Government (KRG). The scene made me a bit nervous about possible Iranian reprisals, so I asked if I could report it. "Certainly," I was told, "it's already all over the local media."

But sure enough, a few days later, unknown assailants attacked a KDP-I office inside Iraqi Kurdistan, killing seven people. The attack was all the more egregious as it took place not near the Iranian border, but in the town of Koy Sanjaq, right in the middle of the Kurdistan region. No one has been publicly charged with the killings, nor has the KRG even publicly blamed them on Iranian agents. The incident chillingly illustrates the nature and reach of Iran's influence in Iraqi Kurdistan: if you cross us too much, we will kill you.

Beyond such extreme but isolated events, the specter of Iran looms very large over the much bigger question of Kurdish independence. Iran continues to voice its firm opposition to this option -- most recently this past week, during a visit of Kurdistan's Islamic party leaders to Tehran. In a telling contrast, for at least the past year, KRG president Masoud Barzani has refused a standing invitation to visit the Iranian capital, reportedly in part because Iran has so far refused to fly the Kurdish flag in official welcome.

In fact, during my recent visit, a top KRG official privately revealed an acute insight into how deeply the Iran factor cuts in this context. Kurdistan's leaders lately aver that they prefer, not unilateral steps toward independence, but negotiations with Baghdad over new terms of coexistence, confederation, or separation. But when they say Baghdad, this official told me, they really mean Tehran. That is because the Kurds see the Iraqi government as essentially subservient to Iran. Whatever Baghdad may ultimately be willing to grant the Kurds will reflect Tehran's decision.

On a more mundane level, Iran exercises considerable direct economic leverage in Kurdistan as well. The region's main economic lifeline, oil, literally runs through Turkey rather than Iran. Desultory negotiations over a new oil pipeline to Iran continue, so far to no practical effect. But other trade with Iran, particularly imports of food staples and other basic consumer goods, is also a key stabilizing factor in the day-to-day economic life of the Kurdistan region. Two-way truck trade in oil products remains significant as well. Iran has been known to close the border, or drastically slow down traffic there, as a form of political signaling and pressure.

Conversely, Kurdish friends in the local business community tell me that Iran has offered them free merchandise (otherwise known as bribes) if they agree to promote or at least turn a blind eye to Tehran's activities in the region. On a much larger level, Tehran is trying to tempt the KRG with talk of a hypothetical pipeline from Kurdish oil fields to Iran. At the same time, it threatens the KRG with talk of a different hypothetical pipeline, this time from Kirkuk directly to Iran -- but bypassing Kurdish control.

The extent of Iranian influence is particularly evident in Sulaymaniyah province, which borders Iran and is dominated politically by the Patriotic Union of Kurdistan (PUK) and its splinter Gorran Party. Both of those parties have closer historical and personal ties to Tehran than does the rival Kurdistan Democratic Party (KDP), based in the western provinces of Erbil and Dahuk near the Turkish border. In 2011, while visiting Sulaymaniyah, I heard a top Gorran official say that in his province alone, "Iranian agents have 700 safe houses." Momentarily stunned by this huge number, I asked, "What are they doing in all those places?!" His laconic answer was instructive: "Well, if I knew the answer to that question, they wouldn't be safe houses, would they?"

Today, Iran's threatening presence in Sulaymaniyah has, if anything, changed further for the worse. Just this week, to cite but one example, an outspoken anti-Iranian member of the Iraqi parliament, Mithal al-Alusi, told the author that he would not even travel to Sulaymaniyah without a whole convoy of bodyguards. More broadly, Iran is exploiting these intra-Kurdish divisions in order to accomplish two related objectives: increase its own influence, through PUK-affiliated and other factional friends, as far afield as the Turkish border; and decrease the KRG's ability to present a unified front in negotiating on behalf of its legitimate interests, whether for eventual independence or merely for more secure political and economic autonomy.

For U.S. policy, especially now that the Trump administration seems poised to take a tougher line toward Tehran, this close but tense relationship between Iraqi Kurdistan and Iran poses an intriguing conundrum. On the one hand, the KRG seems to offer a prime opportunity, with strong local support, to counter and perhaps even roll back Iranian regional influence. Doing so could have ripple effects far beyond the KRG itself, weakening the chain of proxies Tehran has created from Iran through Iraq and on to Syria, Lebanon, and the Mediterranean coast. On the other hand, such a forward U.S. policy would probably require a larger commitment to protect the Kurds from Iranian threats. And it could raise the issue of Kurdish independence as the next logical step in this sequence, with all of the complications that might entail.

That is why, as one senior KRG official put it on my recent visit, "In some short-term sense, it makes life easier for us if the U.S. and Iran are not in a state of active confrontation." Yet if the United States is indeed now determined to stand up more strongly against Iran's regional challenges, while maintaining a crucial ally and buffer against the Islamic State and other violent extremists, Kurdistan would be an excellent place to start. The first step should be a simple, firm assurance to the friendly KRG leadership that Washington will unequivocally back their indigenous efforts to check Iranian subversion, intimidation, and power projection on Kurdish soil. The second step should be a clear U.S. offer to keep a substantial military presence inside the KRG even after victory against the Islamic State -- and even if Baghdad declines a parallel offer. After that, U.S. partnership with the KRG and others in pushing back against Iranian encroachments, not just in Kurdistan but around the region, will become increasingly effective, and decreasingly risky.