The BBC's Daniel Nasaw wants to learn Farsi to get closer to his Iranian-American partner and her family. And nothing but a 33-year-old row between Washington and Tehran is getting in the way.

I was surrounded by Iranians. We were drinking tea in my partner's mother's crowded, sunny living room in Florida. My partner Layla and her relatives were chatting away in Farsi, paying me scant attention.

Were they talking politics or football or the lunch menu? I had no idea.

Suddenly the room fell silent.

Layla's grandmother, a petite, mischievous-eyed woman from Tehran, stared at me in the eye. She addressed me in Farsi. I smiled, wide-eyed. Then the rest of the room erupted into laughter.

If I'm to be the butt of a joke, I declared to myself, I prefer to understand the punchline.

That was four years ago, the day I resolved to learn Farsi. Also known as Persian, it's the rich, ancient tongue of the US's bugbear antagonist, Iran - and Layla's first language.

Image caption Farsi is very, very difficult to learn, but the author believes she's worth the effort

The next time Layla's granny has a laugh at my expense, I thought, by God I'll have a retort.

Layla and I lived next door to one another when we met in Washington in 2008. I had seen her on the block carrying a yoga mat and had noticed her beautiful raven-black hair and her olive skin.

Later, I fell in love with her sense of justice, her quirky sense of humour, and the dignity I imagine comes with her membership of a proud and ancient Persian culture.

Alas, the US and Iranian governments have none of our mutual affection. In a sense, the two countries broke up in 1979 and have been unable to work out their differences.

For much of the 20th Century, Iran was seen as a reliable ally in the American global fight against communism.

While Shah Mohammad Reza Pahlavi held power, Americans hoping to study Farsi could travel to Iran with the Peace Corps or with private industry, or attend several top-quality language programmes in Tehran and elsewhere in the country.

The two countries broke off diplomatic ties during the 1979 revolution and many Iranians, who had been aligned with the Shah or who otherwise found themselves unwelcome in the new Islamic Republic of Iran, fled.

Today, an estimated 470,000 people of Iranian descent live in the US, the vast majority of whom arrived since 1979 or, like Layla, were born to those emigrants.

Layla's parents came to the US separately before the revolution to study. They met here, married, and decided to stay and raise a family. Layla was born a few years later.

After my encounter with her grandmother, I dived into my studies full of Yankee over-confidence.

I was all but certain that she and I would soon be trading one-liners - "A Tehrani, an American and an Arab walk into a tea house..." and the like.

Image caption Plus, he needs all the help he can get

Farsi is an Indo-European language, so although it is much closer to Indo than to Euro, it and English share a long-ago common ancestor.

Its formal grammar is relatively simple: No grammatical gender, irregular verbs or noun declension - the kinds of things that bedevil students of Latin, French and German.

But like English, Farsi has a rich and vast vocabulary, a good part of which was borrowed during a historical confrontation with another great civilisation. English had the Norman invasion; the Persians were conquered by the Arabs in the 7th Century.

And Farsi contains consonants that are not even heard in English: A "kh" familiar to me from Hebrew school; and a back-of-the-oesophagus phoneme, oft rendered "q" in Latin-alphabet transliteration, that rings somewhere among a "g", "k" and French "r".

These sounds render words as distinct to the Iranian ear as "fish" and "dish", but they confound dilettante Americans who misplace them at their peril. The words for coffee and suffocate are dangerously close. I'll offer granny tea next time I see her.

The Farsi words for coffee and suffocate are dangerously close. I'll offer granny tea next time I see her.

Since September 11 and the instability that followed, the number of Americans studying Farsi has climbed dramatically, perhaps because when ambitious students and professionals see Iran in the news, they regard learning Farsi as a way to further their careers.

"When there's tension and escalation, we see the number of students moving up," says Mohamed Elmenshawy, director of languages at the Middle East Institute, the Washington research centre where I study Farsi in the evenings.

"Now, because it's a tense time, we have a good number of students."

Also, the first generation of Iranian-Americans born to post-1979 exiles came of age and began taking Farsi classes - Elmenshawy estimates about 30% of Farsi students at the school have an Iranian background.

Nevertheless, few Americans actually study Farsi, according to the Modern Language Association, which classifies it as a "less commonly taught language".

Image caption In Farsi, 'I love you' is 'doost-at daram'

The number of students enrolled in university courses remains a fraction of those taking Spanish, Japanese, Arabic and even American sign language.

My classes are taught by an architect who spent his formative years in France after fleeing Iran in his youth.

In class, he banters in Farsi with a half-Iranian university student, as I struggle to keep up. The teacher tries to include me in the conversation. I smile and nod.

I'm doing all right, but embarrassing mistakes are made - like the time I wanted to say "American government" but got a vowel wrong and said "your American penis".

"Persian is the easiest foreign language to learn," says Professor Michael Hillmann, a professor of Persian at the University of Texas and author of several language instruction guides. It's easy for him, perhaps. He spent six years in Iran before the revolution.

Immersion, then, that's the key.

But BBC employees are banned from entering Iran. My courageous colleagues on the BBC Persian Service live in exile, their families back home subject to harassment. Iranian border guards even turned away the car programme Top Gear last year.

And the US state department warns that Americans who visit Iran risk arrest and imprisonment there.

Image caption I translated it myself: Iranian regime supporters denounced the BBC and the British in 2009

What about Afghanistan, next door? About half of the Afghan population speaks Dari, a more grammatically formal but mutually intelligible relative.

Yet 11 years into the US-led war there, I doubt I'll be able to find a family in Mazar-e-Sharif to host me for a summer study abroad.

Tajikistan? They speak Farsi. But having absorbed Layla's Iranian chauvinism, I would be loathe to talk to her mother in a Tajik accent.

Layla and I could enforce Farsi-only evenings in our home. But at the end of a long day, the last thing Layla wants to do is chat to me as if to a three-year-old.

So for now, I'll continue my evening classes. I study my vocabulary and I'll watch Iranian film. I'm making some progress - soon I expect I'll be able to read a children's book.

And I'll wait for the day Tehran and Washington patch things up so I can visit Iran - God willing.

Or, as they might say in Iran: Be omid-e Khoda!

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