Secretary of State John F. Kerry came to Israel’s defense Monday amid growing political tensions between the allies, saying that anti-Israeli bias by the United Nations’ top rights panel is undermining its mission.

Kerry’s statements contrast with the Obama administration’s deepening divide with Israeli Prime Minister Benjamin Netanyahu, who plans address a joint meeting of Congress on Tuesday and criticize talks U.S. efforts to reach a deal with Iran seeking to control Tehran’s nuclear program.

But the White House also remains one of Israel’s main backers on the world stage – a relationship that some of Netanyahu’s critics fear could be eroded by his visit to Washington to attack U.S. policies on the Iran negotiations.

“No one in this room can deny the bias against Israel in the U.N. Human Rights Council,” said Kerry, addressing a meeting of the U.N. organization shortly before he was scheduled to join envoys from five other world powers to resume nuclear talks with Iran.

Every year, five or six U.N. resolutions critical of Israel are introduced, Kerry said, singling out for special ridicule one by Syria regarding Israel’s presence in the Golan even as Syrian refugees were fleeing fighting to seek medical treatment in Israel.

U.S. Secretary of State John Kerry, right, shakes hands with Russian Foreign Minister Sergey Lavrov prior to a meeting on March 2, 2015 in Geneva. The meeting came amid continuing tensions over Ukraine and U.S. calls for a full probe into the murder of a prominent opposition figure in Moscow. (Evan Vucci/AFP/Getty Images)

Such resolutions, he said, are self-imposed roadblocks to progress by the U.N.’s highest body dedicated solely to human rights.

“It must be said: the HRC’s obsession with Israel actually risks undermining the credibility of the entire organization,” Kerry added. “It has the potential to limit the good we can accomplish.”

Kerry promised that the United States would work to defeat anti-Israel resolutions it considers “arbitrary.”

“The United States will oppose arbitrary efforts to delegitimize Israel,” he said. “Not just in the U.N. Human Rights Council, but wherever it occurs.”

Kerry’s vigorous defense of Israel came just hours before Netanyahu was scheduled to speak at the annual meeting of the American Israeli Political Action Committee, a major lobbying group.

Netanyahu will argue against Congressional approval of a possible deal with Iran to limit its nuclear program in exchange for sanctions relief. Netanyahu considers any deal that does not deny Iran virtually all nuclear capacity is a bad deal.

The West and its allies fear Iran’s uranium enrichment labs could eventually produce warhead-grade material. Iran claims it only seeks to make nuclear fuel for reactors for energy and medical applications.

Jason Rezaian’s journey has taken him from a childhood in San Francisco to his father’s native Iran. At 37, he became the Washington Post correspondent in Tehran. In July 2014, he was thrown into Iran’s Evin Prison, where he remains, without access to a lawyer. This is his story. (Jorge Ribas/The Washington Post)

In remarks to reporters, Kerry advised critics of the talks to wait until an agreement is actually struck rather than picking apart reported elements of the possible deal.

Kerry did not specifically mention Netanyahu, but the comments appeared aimed at the Israeli prime minister for earlier statements claiming to disclose proposed negotiating points between Iran and world points.

“We are concerned by reports that suggest selective details of ongoing negotiations will be discussed in upcoming days,” he said. “Doing so makes it more difficult to reach the goal that Israel and others say they share – to get a good deal.”

Kerry said an acceptable deal would block any potential pathways Iran could take to develop nuclear weapons down the road, including through covert measures.

“Israel’s security is absolutely is at the forefront of all our minds,” he said. “But . . . so is the security of all the other countries in the region. So is our security in the United States.”

In Washington, Netanyahu also tried to downplay rifts with the White House, telling a pro-Israel lobbying group that his upcoming speech to Congress is not intended as “disrespect” to Obama or his policies.

But he said he breaks with the president over ways to limit Iran’s capacity to one day produce nuclear arms, insisting Israel’s “survival” was at stake.

Earlier Monday, Kerry met Russian Foreign Minister Sergei Lavrov Monday in Switzerland to discuss a range of issues, primarily the status of the Iran nuclear talks, the war in Ukraine and the murder of a prominent political opponent in Moscow.

Kerry and Lavrov met at a luxury hotel under heavy security, as police boats patrolled Lake Geneva just across the street.

Last week, Kerry accused officials in Moscow of lying “to my face” about the conflict raging in Ukraine between Russian-backed rebels and government troops. There was no warmth in the room when the two diplomats first met and shook hands. Neither smiled as they greeted each other, though Lavrov smiled briefly after the cameras were turned off.

Kerry planned to tell Lavrov that the United States expected an investigation into the fatal shooting Friday of Boris Nemtsov to determine not only who pulled the trigger but who may have ordered the assassination of the opponent leader and vocal critic of Russian President Vladimir Putin.

Lavrov on Monday called the killing a “heinous crime which will be fully investigated,” according to the Associated Press. He told the U.N. Human Rights Council in Geneva that Putin is “ensuring special control over this investigation.”

At the same time, however, Lavrov criticized any outside interference in the murder probe, saying that any “attempt to use the heinous killing of Boris Nemtsov for political purposes is despicable.”

The United States insists the murder investigation “must pass muster in the eyes of both the Russian people and internationally,” according to a senior State Department official traveling with Kerry, speaking on condition of anonymity under briefing rules.

The meeting in Geneva came just as the United Nations human rights office issued a report saying that more than 6,000 people have died in eastern Ukraine since the start of the conflict almost a year ago, leading to a “merciless devastation of civilian lives and infrastructure.”

While Russia denies its troops are fighting in Ukraine to aid pro-Moscow separatists, the U.N. cited “credible reports (that) indicate a continuing flow of heavy weaponry and foreign fighters” from Russia.

Daniela Deane in London and Brian Murphy in Washington contributed to this report.