US Secretary of State John Kerry said Thursday he remained hopeful for a ceasefire in the Gaza conflict but declined to predict when.

Kerry, on a visit to India, said he had remained in close contact on the telephone with players in the Middle East to try to end the Israel-Hamas conflict.

"The United States remains hopeful that it is achievable, and the sooner the better," Kerry said of a ceasefire.

"There is no promise in that, but I think everybody would feel better if there was a bona fide effort," Kerry told a joint news conference with Indian Foreign Minister Sushma Swaraj in New Delhi.

Kerry has focused much of his tenure on crises in the Middle East, and returned to Washington just Sunday from a grueling, unsuccessful mission to end the Gaza conflict.

Israel said Thursday it would not pull troops from Gaza until they finish destroying a network of cross-border tunnels, despite sharp United Nations criticism over the Palestinian civilian death toll.

Washington said Thursday it had agreed to restock Israel's dwindling ammunition supplies, despite increasing international concern over the death toll in Gaza, where 1,395 people have been killed in 24 days of violence.

UN figures indicate two-thirds of the victims were civilians. Of the civilian dead, nearly half were women and children.