Israeli airstrikes killed at least 38 Palestinians in Gaza, according to media reports Sunday, as Prime Minister Benjamin Netanyahu was headed to Washington for talks on a ceasefire plan.

Netanyahu is scheduled to meet with U.S. President Donald Trump on Monday to discuss a U.S. proposal for a truce in the 21-month war between Israel and Hamas.

The U.S. proposal for an initial 60-day ceasefire would include a partial release of hostages held by Hamas in exchange for an increase in humanitarian supplies allowed into Gaza, the Associated Press reported.

Netanyahu’s office announced late Saturday that an Israeli negotiating team would travel to Qatar on Sunday for ceasefire talks. But at the same time it said Hamas had requested amendments to the truce proposal that were “unacceptable to Israel.”

The Israeli statement came after Hamas said it is “seriously ready to enter immediately into a round of negotiations” for a ceasefire in Gaza. The Palestinian militant group said in a statement late Friday that it had given a “positive response” to the U.S.-brokered proposal.

Trump said on Friday that there could be a ceasefire deal in the coming week. 

Hezbollah leader Naim Kassem, meanwhile, reiterated on Sunday the militant group’s refusal to lay down its weapons before Israel withdraws from all of southern Lebanon and stops its airstrikes, the AP reported. He spoke in a video address as thousands gathered in Beirut’s southern suburbs to mark the Shiite holy day of Ashoura.