Hamas, the Palestinian armed group, said on Sunday night that it would free Edan Alexander, the last living American citizen held captive in Gaza, just days before President Trump is expected to arrive in the region for the first major foreign tour of his second term.

In a statement, Khalil al-Hayya, Hamas’s lead negotiator, did not say when Mr. Alexander would be released and what, if anything, Hamas would get in exchange. But the Trump administration hoped Mr. Alexander would be released as soon as Monday, said a U.S. official who spoke on the condition of anonymity because of the sensitivity of the talks.

The announcement comes at a pivotal moment for the region. Palestinians have been bracing for a huge escalation of Israel’s renewed ground offensive in Gaza, while the families of Israeli hostages have expressed diminishing hope for a breakthrough to free their loved ones.

Raised in Tenafly, N.J., Mr. Alexander, 21, moved to Israel to serve in the military after high school. He was at a military post on Oct. 7, 2023, when Hamas-led militants stormed across the border in the surprise attack that ignited the war in Gaza.

Alongside some 250 others, Mr. Alexander was abducted and taken to Gaza for use as a bargaining chip in future negotiations with Israel. More than 18 months later, 59 of them remain in the enclave. Dozens of them are presumed dead by the Israeli authorities, including four U.S. citizens.

U.S. officials negotiated directly with Hamas leaders to secure Mr. Alexander’s release, breaking with the traditional American boycott of the group, according to two Palestinians and a diplomat familiar with Hamas decision-making, all of whom spoke on the condition of anonymity due to the sensitivity of the talks.