Gaza negotiators are set to meet in the Qatari capital Doha again on Friday, in an effort to hammer out a ceasefire agreement as Israel continued to slam targets in the Palestinian enclave.
Gaza health officials reported on Thursday that the death toll there had surpassed 40,000 people after more than ten months of fighting.
The round of negotiations opened on Thursday, and the talks would resume on Friday for a second day, Qatari and US officials said.
A US official briefed on the discussions in Doha, who declined to be identified, told Reuters that Thursday's talks were "constructive."
"This is vital work. The remaining obstacles can be overcome, and we must bring this process to a close," US national security spokesperson John Kirby told reporters at the White House.
Israel, meanwhile, pressed its assault on Gaza. Gaza health officials said at least six Palestinians were killed on Thursday night in an Israeli air strike on a house in Jabalia in northern Gaza Strip.
Israeli troops earlier hit targets in the southern cities of Rafah and Khan Younis.
In a statement Hamas politburo member Hossam Badran said Israel's continuing operations were an obstacle to progress on a ceasefire. Hamas officials did not join Thursday's talks.
Badran said the talks must move toward the implementation of a framework agreement accepted previously and achieve a complete ceasefire, withdrawal of Israeli forces, return of displaced Palestinians, and a hostage exchange deal.
"Hamas looks at the ongoing negotiations in Doha regarding a ceasefire and a hostage exchange from a strategic perspective with the goal of ending the aggression on Gaza," he added.
Mediators planned to consult with Hamas' Doha-based negotiating team after the meeting, the US official told Reuters.