Britain has updated a warning to travellers visiting Burma ahead of the elections this year only a week after Washington urged US citizens to “exercise caution…at all times”.

In just over two months Burma will head to the polls for its first elections in 20 years. The British foreign office warned that “the political situation in Burma remains unsettled and tensions could resurface as preparations for the elections due in November 2010 gather momentum”.

The warning comes as the Burmese government takes the first step in tightening its border before the elections, with the newly introduced visa-on-arrival scheme ending on 1 September.

While no official reason has been given, the change in tack is widely seen as an attempt to block foreign ‘undesirables’, such as journalists, from gaining access during the elections, which many have decried as a sham aimed at cementing military rule.

Visas have also been stopped for the hundreds of aid workers in the Irrawaddy delta, which was obliterated by cyclone Nargis in May 2008. A government announcement said only that “the relief period is now over”, although it may also be an attempt to lessen the number of foreigners prior to elections.

The ruling junta is already acutely fearful of an open flow of information leaving the country, and is expected to clamp down on media as the polls near.

The US State Department last week reiterated a warning that Burmese authorities in the past have been “detained, arrested, tried and deported for, among other activities, distributing pro-democracy literature and visiting the homes and offices of Burmese pro-democracy leaders”, the latter likely a reference to a bizarre incident last year in which US citizen John Yettaw swam to the lakeside home-cum-prison of opposition icon Aung San Suu Kyi.

It added that “authorities have warned US embassy officials that those who engage in similar activities in the future will be jailed rather than deported, although this has not yet occurred”.

Moreover, travel restrictions on US officials mean that “US government assistance to US citizens affected by incidents in remote areas of Burma may be difficult”.

Britain echoed the warning, saying that “Consular assistance [to British citizens] in an emergency may…be restricted or delayed”.

From 1 September onwards, visitors will be required to apply for a tourist visa at their local Burmese embassy. This carries with it careful vetting of identity by authorities who use the government’s notorious ‘blacklist’ to weed out and deny visas to those it considers subversive or anti-junta.