Prime Minister Benjamin Netanyahu and his close aides are very nervous about the transition to a new U.S. administration after a four-year honeymoon with Donald Trump. One Israeli official told me it felt like going through detox.

What he's saying: Netanyahu congratulated Biden minutes after he was sworn in, saying in a statement that he looked forward to working together to "continue expanding peace between Israel and the Arab world and to confront common challenges, chief among them the threat posed by Iran."

Between the lines: Netanyahu fiercely opposes Biden's plan to return to the Iran nuclear deal, putting the two are on a collision course.

• Secretary of State designate Tony Blinken said during his confirmation hearing on Tuesday that the U.S. wouldn't rush back into the deal and would consult with Israel and the Gulf states before re-joining.

But that hasn’t reassured Netanyahu and his close aides, who have been concerned to see some of the deal's architects and fiercest advocates join Biden's administration.

• Biden and Blinken are now considering Rob Malley — a former Middle East adviser to Barack Obama who was deeply involved in the talks which led to the 2015 deal — as the administration's Iran envoy, working out of the State Department, Israeli and U.S. officials say.
• A Biden aide said no final decision had been made on a potential appointment. The State Department declined to comment.

The other side: Israeli officials were happy with the choice of Brett McGurk to hold the Middle East file on Biden's National Security Council (NSC).

• McGurk has close relationships with many senior officials in the Israeli security establishment. An Iraq and Syria expert, he's expected to focus much of his work on Iran’s regional activity, an issue of great interest to Israel

On the Israeli-Palestinian issue, which isn't expected to be a high priority for Biden, Blinken conceded in his hearing that he doesn’t expect any progress towards a peace deal in the near future.

• Israeli officials were satisfied with those remarks as well as Blinken's support for Trump's Abraham Accords process and statements that the U.S. would continue to recognize Jerusalem as Israel's capital.
• Unlike Obama and Trump, Biden is not expected to appoint a special envoy for the Middle East peace process. That portfolio will be likely handled by the State Department's assistant secretary for Near East affairs. It's not yet clear whether Blinken wants a career official or a political appointee for that job.
• Jon Finer, who worked on the Israeli-Palestinian issue while on then-secretary of State John Kerry's staff, could also influence the administration's policy in his new role as deputy national security adviser.

Four women will have key roles in handling relations with Israel under Biden:

• Barbara Leaf will be the senior director for Middle East on the NSC, Julie Sawyer will work under Leaf as the director for Israel-Palestine, Dana Stroul will be the deputy assistant secretary of Defense for the Middle East and Mira Resnick will be deputy assistant secretary of State for political-military affairs.
• All four are well known and respected in the Israeli national security and foreign policy establishment.

Flashback: Under Trump, the U.S.-Israel relationship was managed top-down by a small number of officials at the White House and Prime Minister's office.

• The Biden administration is expected to work in a more traditional way, meaning Netanyahu and his aides won’t have almost unlimited access to the president.
• Israel will have to put a new premium on building relationships at lower levels within the NSC, State Department and Pentagon.

What’s next: Separate discussions on how to engage with the Biden administration are being held in the prime minister's office, ministry of defense and foreign ministry.

• But because of political tensions between Netanyahu and his foreign and defense ministers, there have been no interagency meetings and no signs of a united Israeli strategy on issues like Iran and the Palestinians.