US President Donald Trump said on Thursday that he will decide whether to attack Iran within the next two weeks due to a "substantial" chance of negotiations, as Israel and its regional rival traded fire for a seventh day.

White House Press Secretary Karoline Leavitt read out a message from Trump at a briefing, saying there had been "a lot of speculation" about whether the United States would be "directly involved."

"Based on the fact that there's a substantial chance of negotiations that may or may not take place with Iran in the near future, I will make my decision whether or not to go within the next two weeks," Trump said in the statement.

Leavitt would not give details of what had led Trump to believe that negotiations with Iran were possible.

'May do it, may not do it'

Trump had said on Wednesday that Iran had asked to send officials to the White House to negotiate a deal on its nuclear programme and end the conflict with Israel. Iran denied it would do so.

Leavitt said that "correspondence has continued" between the United States and Iran when asked about reports that Trump's special envoy Steve Witkoff had been in touch with Iran's foreign minister.

But she said she was "not tracking" that Witkoff would go to Geneva for talks with Iran.

Trump held his third meeting in three days in the White House's highly secured Situation Room on Thursday as he continued to mull whether to join Israel's bombing campaign.

The US president had said on Wednesday that "I may do it, I may not do it" when asked if he would take military action against Iran.