WASHINGTON — Five months ago, Jared Kushner, President Trump’s son-in-law and senior adviser, began quietly shifting his focus from brokering a peace accord between Israel and the Palestinians to tackling the dire humanitarian crisis in the Palestinian enclave of Gaza.

Now, with Israel and the Hamas militants who control Gaza in a fresh cycle of violence that analysts fear could escalate into a full-blown war, Mr. Kushner and his partner in Middle East peacemaking, Jason D. Greenblatt, are threatening to pull the plug on Plan B.

Declaring that no foreign investors are willing to pour money into Gaza during what they label a Hamas-driven conflict, Mr. Kushner and Mr. Greenblatt, the president’s special representative for international negotiations, are rethinking their efforts to rebuild Gaza’s economy as a way of opening the door to a broader peace accord.

“Hamas has driven Gaza to a state of desperation,” Mr. Kushner said on Sunday. "Provocations will not be rewarded with aid.”