WASHINGTON -- Vice President Joe Biden acknowledged "overwhelming frustration" with Israel's government on Monday and said Prime Minister Benjamin Netanyahu's administration has led Israel in the wrong direction, in an unusually sharp rebuke of America's closest ally in the Middle East.

Biden, in a speech to the advocacy group J Street, offered a grim outlook for peace efforts, reflecting dim hopes for progress during the remainder of the Obama administration. Although he said Israelis and Palestinians shared blame for undermining trust and shirking responsibility, he was emphatic in his critique of Netanyahu's government, suggesting his approach raised "profound questions" about how Israel could remain both Jewish and democratic.

"I firmly believe that the actions that Israel's government has taken over the past several years -- the steady and systematic expansion of settlements, the legalization of outposts, land seizures -- they're moving us and more importantly they're moving Israel in the wrong direction," Biden said.

Get Breaking News Delivered to Your Inbox

He said those policies were moving Israel toward a "one-state reality" -- meaning a single state for Palestinians and Israelis in which, eventually, Israeli Jews will no longer be the majority.

"That reality is dangerous," Biden added.

Biden, who met in March with both Netanyahu and Palestinian President Mahmoud Abbas, said he came away from that trip discouraged about prospects for peace anytime soon. Still, he said the U.S. is obliged to guarantee Israel's security and to "push them as hard as we can" toward a two-state solution despite "our sometimes overwhelming frustration with the Israeli government."

"There is at the moment no political will that I observed from either Israelis or Palestinians to go forward with serious negotiations," Biden said.

The vice president's remarks to J Street, a dovish Israel advocacy group that frequently criticizes Netanyahu, came at the height of a campaign season in which candidates have been scrutinized over their adherence to traditionally stalwart U.S. support for Israel. Ahead of Tuesday's primary in New York, Democratic candidate Bernie Sanders has sparked controversy by saying the U.S. should be even-handed and mustn't always say that Netanyahu is right.

Biden also singled out Palestinian leaders, including Abbas, for declining to condemn specific acts of terrorism carried out against Israelis, in a nod to the seven-month wave of Palestinian stabbings and other attacks. He said he didn't know whether Monday's bus explosion that wounded scores in Jerusalem was a terrorist attack, but added that the U.S. condemns "misguided cowards" who resort to violence.

"No matter what legitimate disagreements the Palestinian people have with Israel, there is never justification for terrorism," Biden said. "No leader should fail to condemn as terrorists those who commit such brutalities."

Biden's tough talk about a key U.S. partner reflected diminishing patience within the White House as President Barack Obama's term nears an end, compounded by deep disagreements over Iran and a strained relationship between leaders. In recent weeks, the Obama administration has left open the possibility that it could support or at least not block a U.N. resolution laying out parameters for a future peace deal, a possibility Israel has railed against.

In another dig at Netanyahu and his Likud party, Biden singled out for praise Stav Shaffir, a young member of Israel's parliament and a Netanyahu critic from the left wing of Israeli politics.

"May your views begin to once again become the majority opinion in the Knesset," Biden said.