Days after President Barack Obama approved a $38 billion Israeli military aid package and attended former president Shimon Peres's funeral in Jerusalem, the White House railed at the construction of 300 housing units on land "far closer to Jordan than Israel."
Warning that the decision jeopardizes the already distant prospect of Middle East peace as well as Israel's own security, press secretary Josh Earnest said Prime Minister Benjamin Netanyahu's word had been called into question.
"We did receive public assurances from the Israeli government that contradict this announcement," he said.
"I guess when we're talking about how good friends treat one another, that's a source of serious concern as well."
The sharper-than-normal comments come as the White House weighs a last-ditch effort to get the peace process back on its feet before Obama leaves office in January.
While serious talks seem unlikely, US officials are weighing the possibility of a major speech outlining the parameters for peace.
Peace efforts have been comatose since a US-led initiative collapsed in April 2014.
A sharper tone over settlements now could help put Israel on notice that future ties are at risk and give Washington more credibility with Palestinians and their Arab allies.
- 'Perpetual occupation' -
In a similarly strong-worded statement, the State Department said building the units "is another step toward cementing a one-state reality of perpetual occupation."
The plan not only undermines hopes for peace with the Palestinians but "is fundamentally inconsistent with Israel's future as a Jewish and democratic state," spokesman Mark Toner said.
Washington has long opposed Israel's policy of building Jewish settlements on land in the West Bank that would be claimed by the Palestinians in any negotiated two-state peace deal.
US officials have adopted a more forceful tone with Netanyahu's government in recent weeks, accusing it of recklessly accelerating construction despite international concern.
The Middle East Quartet -- a contact group comprising the United States, Russia, the European Union and the United Nations -- issued a report in July calling on Israel to halt settlement building.
But the practice has only accelerated since then, Washington says, with new housing blocks being approved, local administrative boundaries moved and unauthorised outposts retroactively approved.
The 300 units the White House was referring to would constitute a new settlement in the heart of the West Bank, roughly halfway between the Palestinian cities of Ramallah and Nablus, according to settlement watchdog Peace Now.
Plans for 98 of the 300 units have so far been advanced, the group said.
The Israeli foreign ministry denied that the planned units amounted to a new settlement, insisting they were to be located in an existing one, although Peace Now said the site was around a kilometre (more than half a mile) away.
"Israel remains committed to a solution of two states for two peoples, in which a demilitarized Palestinian state recognizes the Jewish state of Israel," the ministry said.
Washington has condemned a recent deadly wave of Palestinian attacks on Israeli civilians and police, urging Palestinian leaders to refrain from incitement or provocative language.
Obama and Netanyahu have had an extremely difficult relationship during the last eight years.
The White House was apoplectic when the Israeli leader agreed to address the Republican-controlled Congress to lobby against Obama's signature nuclear deal with Iran.
There were fresh tensions when Netanyahu -- seeking reelection at the time -- said that Palestinians would never get their own state on his watch.
Some considered that pandering to right-wing voters, others said it was Netanyahu showing his true colors.
At last week's funeral for Peres, Obama pointedly spoke of the "unfinished business of peace."
"He believed that the Zionist idea would be best protected when Palestinians, too, had a state of their own," he said of the Nobel Peace Prize winner.
"Of course, we gather here in the knowledge that Shimon never saw his dream of peace fulfilled."