WASHINGTON (TNS) — With Donald Trump tweeting from the sidelines, Secretary of State John F. Kerry condemned Jewish settlement activity under Prime Minister Benjamin Netanyahu as a chief obstacle to Mideast peace, igniting a fresh war of words with the Israeli leader.

Kerry’s lengthy and impassioned address, delivered at the State Department, marked the latest chapter in an unusually bitter public clash between the United States and Israel — and the extraordinary spectacle of the president-elect again inserting himself into a sensitive diplomatic matter before taking office.

In a speech lasting more than an hour, Kerry appealed for a hiatus in Jewish settlement activity in the West Bank and East Jerusalem, called on Palestinian leaders to explicitly denounce terrorist attacks against Israelis, and warned repeatedly that the prospects for a “two-state solution,” with Israel and a Palestinian state existing side by side, were in jeopardy.

Secretary of State John Kerry speaks about Israeli-Palestinian policy, Wednesday, Dec. 28, 2016, at the State Department in Washington. (AP Photo/Andrew Harnik)

“We cannot in good conscience do nothing, and say nothing, when we see the hope of peace slipping away,” he said.

With less than a month until he leaves the State Department, Kerry’s speech was a mainly symbolic gesture, an emblem of last-ditch hopes to restart a U.S.-brokered peace process that collapsed in 2014. Kerry tried again and again to revive the talks, but failed.

Although most of his speech took aim at Israeli policies, Kerry was also critical of Palestinian leaders, saying they needed to do more to condemn specific attacks against Israelis. As an example, he cited the naming of streets and squares for Palestinians who carried out such strikes.

“Murderers of innocents are still glorified,” he said.

Kerry offered up a full-throated defense of President Barack Obama’s Mideast policies, saying the administration had been “Israel’s greatest friend and supporter,” citing enhanced military aid and intelligence sharing.

And he was sharply critical of Netanyahu’s government, saying it was creating a “dangerous dynamic” with continued settlement expansion.

“Time and again we have demonstrated that we have Israel’s back,” said Kerry. But, he added, “friends need to tell each other the hard truths, and friendships require mutual respect.”

After the speech, a visibly angry Netanyahu responded in Jerusalem that Kerry was “obsessively” dwelling on the settlements as part of what he described as a pattern of U.S. bias against Israel.

“If the administration invested the same energy into fighting Palestinian terrorism that it invested in condemning building in Jerusalem, maybe there would have been a better chance to promote peace,” the Israeli leader told reporters.

“Decisions about Israel’s future won’t be made by speeches in Washington,” he added.

Palestinians responded by suggesting they would use a French-convened international conference next month to try to increase Israel’s diplomatic isolation.

Palestinian negotiator Saeb Erekat said Palestinian Authority President Mahmoud Abbas would be willing to resume negotiations “the minute the Israeli government agrees to cease all settlement activities” and implement previous agreements.

As has become his habit, the U.S. president-elect was quick to opine on Twitter — even before Kerry spoke.

Trump tweeted early Wednesday to denounce what he called “disdain and disrespect” shown toward Israel — a reference to the Obama administration’s decision Friday to abstain on a United Nations Security Council resolution that called Israeli settlement activity a flagrant violation of international law.

“Stay strong Israel,” Trump tweeted. “January 20 is fast approaching!” — the date he will take office.

The president-elect has already indicated that he intends to upend long-standing U.S. policy on the Israeli-Palestinian conflict, picking a financial patron of the settlement movement as U.S. ambassador to Israel and pledging to move the U.S. Embassy to Jerusalem from Tel Aviv, a move the Palestinians believe would undermine their statehood hopes.

Obama and Kerry have been the target of intensifying Israeli broadsides since Friday’s vote at the U.N., and even before Kerry spoke, a member of Netanyahu’s Cabinet denounced the U.S. administration’s efforts to influence events in Obama’s last weeks in office.

Speaking to army radio in Israel, Public Security Minister Gilad Erdan called the Obama administration “pro-Palestinian” and Kerry’s planned speech a “pathetic” move. Another Cabinet minister, Naftali Bennett, tweeted against the “establishment of a terror state in the heart of the country.”

Netanyahu’s office has said it would bypass the White House and deal directly with Trump, providing the incoming president with what it said was proof that the Obama administration colluded with the Palestinians to bring forth the U.N. resolution.

In his speech, Kerry vehemently denied that and said Israel had been warned repeatedly that the U.S. would not use its Security Council veto to block the resolution if it were fair and balanced.

Obama’s relations with Netanyahu have long been rocky, but the last few days of exchanges marked some of the harshest public rhetoric in years between the two nations.