The hikers' families say they strayed across the border accidentally
Swiss diplomats have for the first time been allowed to visit three American hikers detained in Iran, Swiss officials have said.
The three have been held since the end of July, when they strayed across the Iranian border from northern Iraq.
A Swiss foreign ministry spokesperson said they had had "direct contact" with the three detained US citizens.
The Swiss government represents US interests in Iran, with whom the US has no formal diplomatic relations.
"I can confirm... that Swiss diplomats have had access to and direct contact with the three Americans citizens concerned in Iran today," a ministry spokesman was reported as telling Reuters news agency.
The trio are thought to have crossed the often poorly-marked Iranian border while hiking in Iraq's Kurdish region.
Relatives said Shane Bauer, Sarah Shourd and Joshua Fattal had made a "regrettable mistake" when they strayed into Iran.
The US state department welcomed the news.
A spokesman said it was "hard to say" whether the visit was connected to upcoming talks in Geneva on Iran's nuclear programme.
Iranian representatives are meeting with the five permanent members of the UN Security Council, plus Germany, in Geneva on Thursday amid rising tensions between Iran and the international community over its nuclear ambitions.
"Obviously we welcome this step, but obviously we are anxious to see Iran seriously engage on Thursday and we look forward to that meeting as well," state department spokesman PJ Crowley said.