The quiet here is eerie. The entire perimeter has been blocked off for over four weeks with lorries full of sand straddling the streets. Normally, the General Assembly would be in full swing, with cavalcades of limousines arriving each day and noisy demonstrators -- Iranians, Puerto Ricans, yes, Afghans and others -- working shifts to chant their grievances across the street. Four weeks ago, my reaction was: "I don't want to be here when Bush addresses the UN; it won't be safe." And that wasn't the first time. During the UN's 50th anniversary celebrations and again during the Millennium Summit, I was angry at being expected to work when the presence of so many heads of state made the UN building an ideal terrorist target. And if the UN becomes identified with Bush's coalition against terrorism, what then?

Right now, the more likely local target would seem to be Donald Trump's latest aberration: "the tallest residential building in the world", which at 80-odd storeys aroused anger and dismay in this neighbourhood when it went up earlier this year, towering over the UN building (a modest 40 storeys). Trump's building now has a huge US flag draped over its top floors -- a challenge to would-be terrorists?

As I pass it, wondering who would be mad enough now to buy a flat there, I try to calculate the odds of it hitting the UN building if it collapsed.

We had an evacuation drill a week ago -- it takes five orderly minutes from my office to the front gate, though I'm sure in an emergency we would take half that time. Would the UN collapse as the World Trade Centre did? I don't know. Many of us have expressed concern that, even now, the security staff don't X-ray our bags when we come into the building. Given that a few years ago a UN employee was allegedly found to be in league with the group that first attacked the WTC, and was plotting to bomb the UN too, such concern might be justified. We don't want to get paranoid, but who knows?

I find myself calculating all sorts of odds now: which airline will be safest for travelling home to the UK? Which NYC tunnel or bridge is least likely to be attacked, which subway line? I'm reminded of living in London in the 70s and redesigning my life to avoid the risk of IRA bombs -- a foolish attempt, since I worked in Westminster.

The visitors' entrance to the UN is closed indefinitely and the garden is off limits. Quite apart from heightening our sense of isolation, this means I can't escape to the garden to look at the autumn foliage and the East River and the cormorants perched on the tiny outcrop of rock just opposite us -- a daily routine that helps preserve my sanity when the General Assembly is in full swing. Otherwise, security is what it would be for the high-level portion of the GA, which normally lasts about a week, but it's been four weeks now, with no traffic noise outside, just the occasional siren. The few pedestrians are very quiet too.

Everyone in the building is very quiet -- not their usual ebullient selves. I feel as I did with my Argentine colleagues during the Falklands war -- I want my Arab and Muslim colleagues to know that I don't support the bombing of Afghanistan, let alone -- God forbid -- an extension of this war to other 'terrorist' countries. In the days after September 11th I was surprised at the apparent lack of emotion here, and angry that non-US staff didn't seem to be upset for the people who died. Now, I just think everyone was wary of expressing anything. After all, there are people from all over the world here and things can polarise so fast. An American colleague, just back from several years in Beirut, has been trying to raise consciousness about Arab, and particularly Palestinian, grievances, and you'd be amazed who gets upset at him. People with otherwise impeccable progressive credentials are in denial about Palestine and suddenly incredibly gung-ho about targeting 'terrorists' (obviously not State terrorists like Ariel Sharon). A Chilean colleague was in Santiago on 11 September -- the anniversary of the 1973 coup. The feeling there was, "Now the Americans know what it's like to see posters of the 'disappeared' on the streets." And who was responsible for the disappearance of thousands of Chileans, if not Nixon, Kissinger and the CIA? When one tots up the thousands, if not millions, of deaths caused by US foreign policy (whether by omission or commission) over the years, it's hard to feel enthusiasm for America's re-emergence from isolationism, and so, of course, we're all cynical about Bush's sudden courting of the UN. Kofi Annan and his wife came around to see us all in our offices in the days after 11 September. What a contrast with Bush and Blair. He's so quiet and unpretentious but exudes moral authority.

There have been counselling sessions for non-US/European staff who may face victimisation outside the UN building. The daughter of an Ecuadorian staff member was told to "go back where she came from" by an American on the street. Anyone with slightly darker skin is at risk, it seems. As a Brit, I have to be careful about expressing support for the Palestinians among my US colleagues and friends, as does my daughter among her school friends. However, everyone I know is pretty much unanimous about despising Bush and the hawks in his government and furious that the many anti-war demonstrations taking place here are getting scant press coverage, for US public support for Bush's campaign is far from universal.

I sit up here in my office unable to concentrate. Normally I'd be inundated with work, but with the GA not really getting going, there's very little to do. I feel under-employed and don't feel like socialising with newly arrived freelance colleagues, some of whom don't seem to realise that we don't want to talk about (and thus relive) our 11 September experiences ad nauseam. I did literally start to feel sick when one person insisted on telling me in detail where and how she'd first learnt the WTC news. So I'm spending much of the day on my email and browsing news sites, which gives me a colossal headache but is also therapeutic.

I was woken by the smoke again this morning. It's been over four weeks, but the rubble burns on. When the wind shifts in the night, you are caught unawares with windows ajar, and you wake in the dark with that familiar sinking feeling in your stomach. How to describe the smell? Like paint burning; like the chemical plants in New Jersey?

I find myself thinking, "Did Germans notice the smell of the death camps? How can you ignore this?"

On the outside, some New Yorkers seem to be ruder than ever and the initial camaraderie seems to have evaporated, though it presumably continues at 'ground zero'. I went to see a friend newly returned to Tribeca from three weeks' evacuation. The quiet down there is eerie too. This used to be a bustling neighbourhood, but the subway now ends abruptly and taxis are not allowed through. Returning residents are trying to support the local economy -- and each other -- by going out every night, but many -- artists, musicians, home-based workers -- have no livelihood any more. I feel guilty being able to distance myself, to return home to an untouched neighbourhood and momentarily forget the bodies lost under the rubble only a mile away.

I'm sure we're all feeling this insecurity and I'm sure it will eventually abate, because we have to go on living here. But for now I'm exhausted and fearful. I wish I could leave. I love this city, but places that were special to me -- the long walk down the Hudson River on the west side of Manhattan, with the water sparkling in the sun and the harbour mouth opening out before me, the children playing in the parks and playgrounds of Battery Park City, and the spectacular sunsets -- will never look or feel the same.