Washington remains prepared to engage with Tehran this week, but any meaningful discussions must address Iran's ballistic missile capabilities, support for armed groups across the Middle East, nuclear activities and domestic human rights practices, US Secretary of State Marco Rubio said on February 5.

Speaking to reporters in Washington, Rubio acknowledged confusion over the location of planned February 6 talks, noting that conflicting reports had emerged with the venue changing from Istanbul to Muscat.

"We thought we had an established forum that had been agreed to in Turkey that was put together by a number of partners who wanted to attend and be a part of it. I saw conflicting reports yesterday from the Iranian side saying that they had not agreed to that, so that's still being worked through," Rubio said.

Rubio outlined four key areas that Washington believes must form part of any substantive negotiation.

"In order for talks to actually lead to something meaningful, they will have to include certain things, and that includes the range of their ballistic missiles. That includes their sponsorship of terrorist organisations across the region. That includes the nuclear programme. And that includes the treatment of their own people," he said.

Rubio linked Iran's economic difficulties to what he described as resource allocation towards regional activities.

"The fundamental problem Iran faces, is that what people are on the streets complaining about, this regime cannot address… because it's economic. One of the reasons why the Iranian regime cannot provide the people of Iran the quality of life that they deserve is because they're spending all their money and resources… sponsoring terrorism," he said.

He said the Trump administration does not view diplomatic engagement as either a concession or a form of legitimisation. "President Trump is willing to talk to and meet with and engage with anyone in the world. We don't view meetings as a concession [or]… legitimisation," Rubio said.

"If the Iranians want to meet, we're ready. They've expressed an interest in meeting and talking. If they change their mind, we're fine with that too… I'm not sure you can reach a deal with these guys, but we're going to try to find out," he added.