LONDON -- Israeli Prime Minister Benjamin Netanyahu's office on Sunday said the country imposed a blockade on all humanitarian aid heading into the Gaza Strip, following the expiry of phase 1 of Israel's ceasefire deal with Hamas and with negotiations regarding phase 2 still ongoing.

"Prime Minister Netanyahu has decided that, as of this morning, all entry of goods and supplies into the Gaza Strip will cease," Netanyahu's office said, accusing Hamas of refusing to accept the outline for continued talks set out by President Donald Trump's Middle East envoy Steve Witkoff.

"Israel will not allow a ceasefire without the release of our hostages," the statement said. "If Hamas continues its refusal, there will be further consequences."

Hamas, meanwhile, said in a statement that "Netanyahu's decision to stop humanitarian aid is cheap blackmail, a war crime and a blatant coup against the agreement."

"We reaffirm our commitment to implementing the signed agreement in its three stages and we have repeatedly announced our readiness to begin negotiations for the second stage of the agreement," the group added, calling on the U.S. "to stop its bias and alignment" with Israel.

This is a developing story. Please check back for updates.

ABC News' Jordana Miller and Nasser Atta contributed to this report.