Nuclear talks between the United States and Iran are expected to take place in Oman ‍on Friday, a regional diplomat said, with a possible confrontation looming as US President Donald Trump builds up forces in the Middle East.

Trump has warned that “bad things” would probably happen if a deal could not be reached, ratcheting up pressure on the Islamic Republic in a stand-off that has led to mutual threats of air strikes and stirred fears of escalation into a wider war.

Iran has said it will not ⁠make concessions on its formidable ballistic missile programme, calling that a red line in negotiations.

Tehran, which says it replenished its stockpile of ballistic missiles since coming under attack from Israel last year, has warned that it will unleash its missiles to defend the Islamic Republic if its security is under threat.

The Trump administration agreed to an Iranian request to move the talks from Turkey and negotiations were still ongoing about whether Arab and Muslim countries from the region would join the talks in Oman, Axios reporter Barak Ravid said on Tuesday, citing an Arab source.