Donald Trump has complained that Japan would not have to help if the US were attacked, suggesting citizens of the allied country "can watch it on a Sony television".

Speaking to Fox Business during a rambling telephone interview, the president said: “If Japan is attacked, we will fight World War III. We will go in and protect them with our lives and with our treasure.

"But if we’re attacked, Japan doesn’t have to help us. They can watch it on a Sony television."

The statement is the latest in a series made by Mr Trump bemoaning existing military agreements with Japan.

Mr Trump was referring to a decades-old treaty that guarantees US aid to Japan if the east Asian nation is ever attacked.

Tensions high as Trump approves new Iran sanctions: In pictures Show all 17 1 /17 Tensions high as Trump approves new Iran sanctions: In pictures Tensions high as Trump approves new Iran sanctions: In pictures Iran claims that in this picture released by Iran state TV, their surface-to-air missile is seen as it shoots down a US surveillance drone EPA Tensions high as Trump approves new Iran sanctions: In pictures This photo shows US RQ-4A Global Hawk unmanned surveillance drone. A drone of this model was shot down by Iran on Thursday 21 June AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures An oil tanker is on fire after it was subject to a suspected attacked at the Gulf of Oman on June 13. The US has blamed Iran for the attack Reuters Tensions high as Trump approves new Iran sanctions: In pictures Iran claims that in this picture released by Iran state TV, debris from the downed US drone is seen after it was recovered from Iranian waters AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures Smoke billows from an oil tanker after it was subject to a suspected attacked at the Gulf of Oman on June 13 Reuters Tensions high as Trump approves new Iran sanctions: In pictures US President Trump holds up a signed executive order to increase sanctions on Iran on 24 June AP Tensions high as Trump approves new Iran sanctions: In pictures Iranian President Rouhani stated in a televised address that the White House is "afflicted by mental retardation" following the increase in sanctions on 25 June EPA Tensions high as Trump approves new Iran sanctions: In pictures An Iranian navy boat tackles the fire on the Norwegian owned Front Altair oil tanker after it was hit in a suspected attack AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures Iran claims that in this picture released by Iran state TV, debris from the downed US drone is seen after it was recovered from Iranian waters AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures Smoke billows from an oil tanker after it was subject to a suspected attacked at the Gulf of Oman on June 13 Reuters Tensions high as Trump approves new Iran sanctions: In pictures A screenshot from a video released by the US Department of Defense that the US claims to show Iranian removing an unexploded limpet mine form the hull of the Japan-owned ship that was attacked in the Gulf of Oman on June 13 Getty Tensions high as Trump approves new Iran sanctions: In pictures An item reportedly found on the Japan-owned oil tanker that was attacked on June 13 in the Gulf of Oman AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures A handout photograph from the US Department of Defense shows a composite material that the US claim was left behind on the hull of the Japan-owned oil tanker following the removal of an unexploded limpet mine Getty Tensions high as Trump approves new Iran sanctions: In pictures A view from the cabin of an Iranian navy boat as it tackles the fire on the Norwegian owned Front Altair oil tanker after it was hit in a suspected attack EPA Tensions high as Trump approves new Iran sanctions: In pictures Release by US government A picture released by U.S. Central Command shows damage to the hull of the oil tanker Kokuka Courageous. The picture suggests that the ship is 'likely' to have been hit by a mine as the US Secretary of State Mike Pompeo moves to blame Iran for the suspected attack Reuters Tensions high as Trump approves new Iran sanctions: In pictures Smoke billows from an oil tanker after it was subject to a suspected attacked at the Gulf of Oman on June 13 Reuters Tensions high as Trump approves new Iran sanctions: In pictures Release by US government A picture released by U.S. Central Command shows damage to the hull of the oil tanker Kokuka Courageous. The pictures suggests that the ship is 'likely' to have been hit by a mine as the US Secretary of State Mike Pompeo moves to blame Iran for the suspected attack EPA

A Bloomberg report suggested the president was considering withdrawing from the accord, which has been in place since the Second World War.

Mr Trump regards the treaty as one-sided, three sources were quoted by Bloomberg as saying.

However, he is yet to take any steps towards ending the agreement and such a move is highly unlikely, the report said, citing people familiar with the matter.

Mr Trump has also talked about seeking compensation for relocating the US base in Okinawa, Bloomberg said.

The two countries are engaged in trade negotiations, with the Trump administration seeking to lower America's trade deficit and boost exports to its major trading partners.

The president has previously said he is unhappy with Japan's trade surplus and wants a two-way agreement to address it.

On Tuesday he railed against other countries' apparent reliance on US military power in the Middle East, singling out Tokyo and Beijing.

"Why are we protecting the shipping lanes for other countries (many years) for zero compensation," he wrote.

Donald Trump shakes hands with Shinzo Abe during a speech to Japanese and US troops in Yokosuka, south of Tokyo, in May (Reuters)

The threat of war in the region has intensified since a US drone was shot down last week.

Asked about the prospect of a conflict in the same Fox interview, he said: "I hope we don't but we're in a very strong position if something should happen.