The Hamas announcement that it will delay the next planned release of Israeli hostages from Gaza has threatened a fragile truce that’s seen as having the potential to wind down 16 months of war.

Hamas has threatened to postpone the next hostage release scheduled to take place in Gaza on Saturday “until further notice,” accusing Israel of breaking the ceasefire deal.

On Monday, the Gaza ceasefire was thrown into doubt after Hamas said it would stop releasing hostages, accusing Israel of violating the agreement. Israel's defense minister said Hamas' announcement violated the deal. The military is at the highest level of readiness in Gaza and for domestic defense.