U.S. Envoy to the Middle East Steve Witkoff has delayed a visit to the region, scheduled to start Wednesday, Israeli and American outlets reported Tuesday.

Citing an Israeli source familiar with the details, the Israeli newspaper Haaretz reported that the reason behind the postponement of the visit is the delay in freeing Palestinian prisoners held in Israeli jails. However, the American news website Axios reported that Witkoff is delaying his trip to the Middle East by a few days due to U.S. diplomatic efforts on Russia and Ukraine.

Israel announced on Sunday that it is delaying the release of Palestinian prisoners — planned as part of the fragile cease-fire in Gaza — until Hamas guarantees an end to the “humiliating ceremonies” for released hostages.

Earlier on Tuesday, the Israeli newspaper Yedioth Ahronoth reported that Witkoff is not expected to arrive in the region on Wednesday, despite his statements in previous interviews, without specifying the reason. Citing sources familiar with the details, Yedioth Ahronoth added that a date for his arrival in the region and Israel has not yet been set.

Witkoff said on Sunday that he was headed to the Middle East this week to discuss an extension to phase one of the Israel-Hamas peace deal.

Palestinian armed group Hamas on Sunday said Israel had gravely endangered the five-week-old Gaza truce by delaying the release of Palestinian prisoners under the deal because of the manner in which Israeli hostages had been freed.

The first phase of the truce ends early in March and details of a planned subsequent phase have not been agreed.