The US is planning to establish a diplomatic presence in Tehran for the first time in 30 years, a remarkable turnaround in policy by president George Bush who has pursued a hawkish approach to Iran throughout his time in office.

The Guardian has learned that an announcement will be made in the next month to establish a US interests section in Tehran, a halfway house to setting up a full embassy. The move will see US diplomats stationed in the country.

The news comes at a critical time in US-Iranian relations. After weeks that have seen tensions rise with Israel conducting war games aimed at Iran and Tehran carrying out long-range missile tests, a thaw appears to be under way.

The White House announced today that William Burns, a senior state department official, is to be sent to Switzerland on Saturday to hear Tehran's response to a European offer aimed at resolving the nuclear standoff.