The White House is seriously considering an Iranian proposal for indirect nuclear talks, while at the same time significantly boosting US forces in the Middle East in case President Donald Trump opts for military strikes, two US officials tell Axios, the latter reports.

"After the exchange of letters we are now exploring next steps in order to begin conversations and trust building with the Iranians," one official said.

The White House is still engaged in an internal debate between those who think a deal is achievable and those who see talks as a waste of time and back strikes on Iran's nuclear facilities.

In the meantime, the Pentagon is engaged in a massive buildup of forces in the Middle East. If Trump decides the time is up, he will have a loaded gun at the ready.

The US official said the Trump administration thinks direct talks would have a higher chance of success, but isn't ruling out the format the Iranians proposed and doesn't object to the Omanis serving as mediators between the countries, as the Gulf state has in the past.