Diplomats at the US mission to the EU can no longer buy office supplies or travel to conferences, as the US "shutdown" begins to bite the state department.

The shutdown started on Tuesday (1 October) after opposition Republican party congressmen refused to endorse a new budget.

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They did it in an effort to block US President Barack Obama from passing a law on more affordable healthcare.

In the US, it has put the best part of a million civil servants on unpaid leave and led to museums and parks being closed.

But it is also beginning to affect US diplomacy.

Obama on Wednesday cut short a tour to Asia due to the problem.

A European Commission spokeswoman the same day said EU-US talks on how to enforce new US commodity trading rules have suffered.

She said that single market commissioner Michel Barnier sent a letter to the Commodity Futures Trading Commission (CFTC) in Washington prior to the budget crunch, but "we haven't got a reply … yet."

She noted there is contact at "senior political level."

But she added the CFTC is closed for now, meaning "there is no contact at technical, official level at this time," in a development which she described as "problematic."

The EU, next week, is also planning to hold the next round of talks on creating a trans-Atlantic free trade area.

According to a US state department paper which sets out guidelines on the shutdown, travel by diplomats is still permitted for "negotiation of major treaties."

But on a more day-to-day level, a US diplomat in Brussels told EUobserver: "Our mission has curtailed activities in accordance with the document."

The memo notes that representatives of the world's only superpower must stop "purchases of equipment, services, or supplies."

It says: "No new travel should be arranged; no one should make new arrangements to attend conferences" and "no new offers of employment may be made."

It also says staff should not organise cocktail parties or other "representational events."

It tells them not to ask for overtime and it says that petty cash expenses "may be filed, but no money can be disbursed."

Meanwhile, if you want a visa for US travel, you are better off applying at one of America's larger embassies, just in case.

The US memo noted that: "consular operations domestically and overseas will remain 100 percent operational as long as there are sufficient fees to support operations."

But it added: "If a passport agency is located in a government building affected by a lapse in appropriations, the facility may become unsupported."