Secretary of State Antony J. Blinken hurried into a bunker as air raid sirens wailed in Tel Aviv on Monday, in the most dramatic moment of a whirlwind — and unusually chaotic — Middle East tour for America’s top diplomat.

After his second visit to Israel in five days, Mr. Blinken was scheduled to land in Amman, Jordan, on Monday night, but he ended up stuck in a marathon overnight negotiation session in Tel Aviv, and his next destination was uncertain. A trip originally scheduled for two days has now extended into its sixth, with 10 stops and counting.

For an official whose travel schedule is meticulously planned and rarely revised, Mr. Blinken’s frenetic journey has underscored the scale and complexity of the diplomatic crisis he faces.

Mr. Blinken is at once trying to show U.S. support for Israel after it was attacked by Hamas on Oct. 7; limit Arab criticism of Israel’s military response; win the freedom of hostages held by Hamas in Gaza; and prevent an escalation of the conflict, perhaps to include Hezbollah and Iran, that might draw in the United States.

It has been a grim voyage for Mr. Blinken, who at times appeared haunted as he described the slaughter of Israeli citizens and a growing humanitarian crisis in Gaza.

Speaking to reporters in Cairo on Sunday, two days after his first stop in Israel, Mr. Blinken conceded that things had become a blur even for him. “I think I’ve lost track” of how many countries he had visited, Mr. Blinken said, before correctly putting the count at seven since his departure from Washington on Wednesday afternoon: Egypt, Bahrain, Qatar and the United Arab Emirates, plus two stops each in Israel, Jordan and Saudi Arabia.

For State Department veterans, Mr. Blinken’s travel was reminiscent of a recent predecessor. John Kerry, who was secretary of state during the Obama administration, frequently extended and improvised his trips — even changing destinations midflight, in what was branded “seat-of-the-pants diplomacy.” Not so Mr. Blinken, who typically travels from Monday to Friday, returning in time to spend the weekend at home with his two young children.

The ad hoc nature of the trip began just days after the massacres by Hamas. Mr. Blinken immediately moved up a visit to the region that he had planned for the following week. The State Department announced that he would depart on Oct. 11 for Israel and Jordan, and return on Friday, Oct. 13.

That plan was soon torn up as State Department officials, in consultation with the White House, expanded Mr. Blinken’s itinerary to include several other major capitals.

“Henry Kissinger’s 33-day trip to reach an Israeli-Syrian disengagement accord following the 1973 October War holds the Middle East shuttle record,” said Aaron David Miller, a senior fellow at the Carnegie Endowment for International Peace and a former longtime State Department Middle East negotiator. “Blinken’s recent wild ride through the region doesn’t quite compare. But it does reflect the uncertainty and chaos of a crisis the administration didn’t see coming and the complexity of the challenges it faces going forward.”

“From here on in,” he added, “the secretary might want to pack a few extra shirts. If the administration wants to make a difference in this region, there are likely going to be more than few wild rides in his future.”

Making a difference will not be easy. Mr. Blinken has not yet succeeded in one of his goals: securing the free passage of American citizens in Gaza through a border crossing into Egypt. Hundreds remained stuck at the sealed border on Monday.

It is not for want of trying. After their arrival in the region, on Thursday, Mr. Blinken and his aides nailed down their schedule for the next day: four countries in one day, from Jordan to Qatar to Bahrain to Saudi Arabia.

They sometimes improvised on the transportation: To get from Tel Aviv, their first stop, to Amman, they took a C-17 U.S. military plane that looped over Cyprus after having sent the usual Boeing 757 Air Force plane ahead so the crew could rest while the American diplomats met with Israeli officials.

In Jordan, Mr. Blinken met with King Abdullah II in his palace and then with Mahmoud Abbas, the head of the Palestinian Authority, in a villa. In Qatar, Mr. Blinken held a joint news conference in a lavish government building with the prime minister. In Bahrain, he spoke to the prime minister, Crown Prince Salman bin Hamad Al Khalifa, in a V.I.P. airport lounge as royal guards in dress uniforms flanked a red carpet on the tarmac outdoors.

To squeeze in meetings, Mr. Blinken took a quick day trip from Riyadh to the United Arab Emirates on Saturday and then back to the Saudi capital again. On Saturday night, he prepared to meet with Crown Prince Mohammed bin Salman, the country’s de facto leader who has regained a measure of diplomatic legitimacy less than three years after the Biden administration released intelligence finding him responsible for the 2018 killing and dismemberment of the Saudi Washington Post columnist Jamal Khashoggi.

That meeting introduced a new element of uncertainty. Reporters traveling with Mr. Blinken were told to be ready at any minute to leave their hotel in the secretary’s motorcade for an audience with the crown prince, the region’s most powerful Sunni Muslim ruler.

The hours dragged on, from midnight to 2 a.m. and then 4 a.m. Finally, the prince agreed to meet Mr. Blinken after 7:30 a.m. on Sunday at his private farm residence. (The journalists, who had stayed up almost all night, were ultimately denied access.)

Officials said it was typical for the prince to keep even important visitors waiting. Still, it was a rare and most likely frustrating experience for a sleep-deprived Mr. Blinken, who is used to foreign officials accommodating his schedule.

At noon on Sunday, it was off to Egypt — supposedly Mr. Blinken’s last stop before returning home. “I know that this is the last of your big tour in the region,” Egypt’s president, Abdel Fattah el-Sisi, told Mr. Blinken at the start of their meeting in Cairo.

Not so fast. After speaking to President Biden, Mr. Blinken added a return trip to Israel to his schedule. He spent the night in Jordan before flying back to Tel Aviv on Monday morning and driving on to Jerusalem to see Prime Minister Benjamin Netanyahu again.

By this time, State Department officials had begun whispering about Mr. Biden possibly visiting Israel this week. Plans for a Monday return to Washington were scratched. The new plan was to fly back to Jordan after negotiations with Israeli leaders over humanitarian aid to Palestinians, and everyone would wait there for further instructions.

In Jerusalem on Monday, between meetings with Israeli leaders, Mr. Blinken made an unscheduled stop at the residence of the American ambassador, popping in to borrow a secure line for a call to Washington. Shortly beforehand, the White House had announced that Mr. Biden was canceling a trip to Colorado that day for a national security meeting — perhaps the same one that Mr. Blinken was calling into.

Mr. Blinken’s trip has also been charged with an unusual current of danger. Security officers who normally wear suits sported body armor and helmets while guarding his plane during his stops in Israel.

On Monday, right after Mr. Blinken’s convoy left Jerusalem, air sirens sounded there, indicating incoming rockets or missiles. Everyone in the city ran for shelter. Sirens sounded too in Tel Aviv. Officials and journalists in the convoy between the two cities were told to race from the cars if sirens sounded and lie down on the ground at roadside.

After Mr. Blinken met with Mr. Netanyahu and his war cabinet around 7 p.m. at the Kirya military base in Tel Aviv, sirens sounded again. The traveling journalists and Israeli soldiers standing outside dashed into a stairwell indoors.

Mr. Blinken and Mr. Netanyahu were meeting in the prime minister’s office in the Shimon Peres House on the base when the sirens sounded. Mr. Blinken and the Israeli officials ducked into a bunker for five minutes. They then walked to a command center to continue their meeting on humanitarian aid, which was punctuated by a third siren before going into early Tuesday morning with no end in sight — far longer than originally planned.