Planning for the visit had been under way for months with U.S. officials, four of the sources said.

Khan's decision to request the warrants upended the plans backed by Washington and London for the prosecutor and his team to visit Gaza and Israel. The court was set to gather on-site evidence of war crimes and offer Israeli leaders a first opportunity to present their position and any action they were taking to respond to the allegations of war crimes, five sources with direct knowledge of the exchanges told Reuters.

Khan's request for a warrant for Israeli Prime Minister Benjamin Netanyahu - the court's first attempt to detain a sitting, Western-backed head of state - also flew in the face of efforts the U.S. and Britain were leading to prevent the court from prosecuting Israeli leaders, the sources said.

The two states have said the court has no jurisdiction over Israel and that seeking warrants would not help resolve the conflict.

Khan's office told Reuters the decision to seek warrants was, in line with its approach in all cases, based on an assessment by the prosecutor that there was enough evidence to proceed, and the view that seeking arrest warrants immediately could prevent ongoing crimes.

Reuters is the first to report in detail about the planned trip and the repercussions of its cancellation.

Khan had for three years been working to improve relations with the U.S., which is not a member of the court. He had asked Washington to help put pressure on its ally Israel – also not a court member – to allow his team access, four sources said.

His move has harmed operational cooperation with the U.S. and angered Britain, a founding member of the court, the sources said.

A senior U.S. State Department official said Washington continued to work with the court on its investigations in Ukraine and Sudan, but three sources with direct knowledge of the U.S. administration's dealings with the court told Reuters cooperation has been damaged by Khan's sudden action.

They said problems have played out in preparations for new indictments of suspects in Sudan's Darfur and the apprehension of fugitives. Two of the sources said one operation to detain a suspect, which they declined to describe in detail, did not go ahead as planned due to the loss of key U.S. support. All the sources expressed concerns Khan's action would jeopardise cooperation in other ongoing investigations.

However, Khan's sudden move has drawn support from other countries, exposing political differences between national powers over the conflict and the court. France, Belgium, Spain and Switzerland have made statements endorsing Khan's decision; Canada and Germany have stated more simply that they respect the court's independence.

The world's war crimes court for prosecuting individuals, the ICC does not have a police force to detain suspects, so it relies on 124 countries that ratified the 1998 Rome treaty that founded it. Non-members China, Russia, the U.S. and Israel sometimes work with the court on an ad hoc basis.

A FEW HOURS' NOTICE

Khan personally decided to cancel the visit to the Gaza Strip, Jerusalem and the West Bank city of Ramallah, which was due to begin on May 27, two of the sources said.

Court and Israeli officials were due to meet on May 20 in Jerusalem to work out final details of the mission. Khan instead requested warrants that day for Netanyahu, Israeli Defence Minister Yoav Gallant and three Hamas leaders -- Yahya Sinwar, Mohammed Deif and Ismail Haniyeh.

A U.N. official, speaking on condition of anonymity, confirmed that initial discussions had taken place regarding a visit to Gaza by Khan, covering security and transportation.

Flight tickets and meetings between senior-level court and Israeli officials were cancelled with just hours of notice, blindsiding some of Khan's own staff, seven sources with direct and indirect knowledge of the decision said.

The U.S. State Dept. official said that abandoning the May visit broke from the prosecution's common practice of seeking engagement with states under investigation. Three U.S. sources said, without providing details, that Khan's motive to change course was not clearly explained and the about-face had hurt the court's credibility in Washington.

Khan's office did not directly address those points but said he had spent the three previous years trying to improve dialogue with Israel and had not received any information that demonstrated "genuine action" at a domestic level from Israel to address the crimes alleged.

Khan "continues to welcome the opportunity to visit Gaza" and "remains open to engaging with all relevant actors," his office said in an email.

Senior Hamas official Basem Naim told Reuters Hamas had no prior knowledge of Khan's intentions to send a team of investigators into Gaza.

Netanyahu's office and the Israeli Foreign Ministry declined to comment.

The war in Gaza erupted after Hamas-led militants stormed into southern Israel on Oct. 7, killing 1,200 people and taking about 250 hostage. Nearly 38,000 Palestinians have been killed in Israel's ground and air campaign, Gaza's health ministry says.

WASHINGTON BLINDSIDED

The ICC admitted "the State of Palestine" in 2015, and Khan says his office has jurisdiction over alleged atrocity crimes committed since Oct. 7 by Palestinians in Israel and by anyone in the Gaza Strip. Neither the U.S. or Britain recognise the Palestinian state, so they dispute the court's jurisdiction over the territory.

Even though Washington and London argue that the court has no jurisdiction in this situation, they were talking to Israel to help prosecutor Khan arrange the visit, four sources close to their administrations told Reuters.

The sources said they had been aware that Khan might seek warrants for Netanyahu and other high-level Israeli officials: Since at least March, Khan or members of his team had been informing the governments of the U.S., UK, Russia, France and China about the possibility of bringing charges against Israeli and Hamas leaders.

A diplomatic source in a Western country said, without giving details, there was a diplomatic effort under the radar to try to convince the ICC not to take this path.

"We worked hard to build a relationship of no surprises," said one U.S. source, who asked not to be named because of the sensitivity of the case.

Blinken on May 21 called Khan's decision "profoundly wrong-headed," saying it was out of line with the process he expected and would complicate prospects for a deal on freeing hostages or a ceasefire. He told a Senate appropriations committee he would work with Republicans to impose sanctions against ICC officials.

On the same day, Cameron told parliament Kahn's move was mistaken.

In private, he responded furiously to the change of plan, calling it "crazy" because Khan's team had not yet visited Israel and Gaza, and threatening in a phone call with Khan to pull Britain out of the court and cut financial support to it, three sources with direct knowledge of the discussion said. A foreign office official declined to comment on the phone call or on Britain's relationship to the court.

In June, the ICC allowed the UK to file a written submission outlining its legal arguments that the ICC does not have jurisdiction over the case. The issue of the court's jurisdiction divides both members and non-members of the court.

The U.S. has a fraught relationship with the court. In 2020, under the former U.S. President Donald Trump, Washington imposed sanctions against it, which were dropped under President Joe Biden.

Khan's office said he "has made significant efforts to engage with the United States in recent years in order to strengthen cooperation, and has been grateful for the concrete and important assistance provided by U.S. authorities."