WASHINGTON -- The White House said Monday the U.S. is helping from afar as thousands of Americans left behind in Sudan seek to escape fighting in the east African nation, after the U.S. Embassy evacuated all of its diplomatic personnel over the weekend and shut down.

President Joe Biden's national security adviser, Jake Sullivan, defended the decision not to keep U.S. forces or diplomats in Sudan to help its citizens evacuate as several U.S. allies did and as the U.S. has often done in conflict zones in the past.

Instead, Sullivan told reporters, the U.S. was now remotely assisting Americans trying to flee the country by road.

U.S. assistance on Monday included helping Americans link up with convoys of foreigners now attempting to make it through fighting toward safety on Sudan's eastern border. The U.S. also is placing intelligence, surveillance and reconnaissance assets over the route from the capital, Khartoum, to the country's main seaport, the Port of Sudan, to scope out safety threats, Sullivan said.

U.S. Secretary of State Antony Blinken said he had helped broker a 72-hour cease-fire to begin late Monday. It would extend a nominal truce coinciding with a Muslim holiday that brought almost no reduction in fighting but helped to facilitate the evacuations.

Sullivan said convoys with Americans in them were beginning to arrive at Port of Sudan on the Red Sea and the U.S. was working with neighbouring countries to get them safely over the border.

Sudan's conflict involves two rival military leaders, the armed forces chief, Gen. Abdel-Fattah Burhan, and the head of the Rapid Support Forces paramilitary group, Gen. Mohammed Hamdan Dagalo, who 18 months ago joined forces to derail the nation's hoped-for transition to democracy.

On April 15, the two began battling between themselves for control of the country. The violence has killed hundreds and left millions of Sudanese seeking safety amid explosions, gunfire and armed fighters looting shops and homes.

Foreign governments have been airlifting hundreds of their diplomats and other citizens to safety as Sudan has spiralled into chaos.

In dramatic evacuation operations, convoys of foreign diplomats, teachers, students, workers and their families from dozens of countries have wound past combatants at tense front lines in Khartoum to reach extraction points.

Others have driven hundreds of miles to Sudan's east coast. A stream of European, Mideast, African and Asian military aircraft flew in all day Sunday and Monday to ferry them out.

France, Germany, Italy, Japan, Jordan, the Netherlands, Saudi Arabia, South Korea, Spain and Turkey are among the countries that have diplomats or troops in the country to evacuate their citizens and those of other countries. That is in contrast to a Biden administration decision that the situation was too dangerous to help private American citizens get out.

On Twitter over the weekend, some Saudis tweeted photos of evacuated Saudi citizens arriving in the Saudi port city of Jeddah and mocked the cautious U.S. response.

Saudi Arabia said Monday its Navy has evacuated 357 civilians from 27 countries, including two Americans.

On Sunday, U.S. special operations forces evacuated Americans from the U.S. Embassy, sweeping in and out of the capital with helicopters on the ground for less than an hour. No shots were fired and no major casualties were reported. U.S. officials said members of the Navy's elite Seal Team 6 were the main force in the evacuation, using helicopters piloted by the Army's 160th Special Operations Aviation Regiment.

In Sudan, an estimated 16,000 private U.S. citizens are registered with the embassy as being in Sudan. The figure is rough because not all Americans registered with the embassy or notified the embassy when they departed.

Sullivan reiterated that the administration continues to look at "every conceivable option" to help Americans get out of Sudan but is not considering troops.

"It is not standard practice for the United States to send in the U.S. military" to extract American citizens from war zones, Sullivan said. "We didn't do it in Libya. We didn't do it in Syria. We didn't do it in Yemen, and no we didn't do it in Ukraine. Afghanistan was a unique case involving the end of the 20-year war that the United States was centrally involved in."

However, Sullivan omitted several other recent instances in which U.S. forces deployed to get American citizens out of danger in foreign wars.

In 2006, the State Department and Department of Defense cooperated in one of the largest evacuations of Americans in modern times, using helicopters, warships and U.S.-contracted commercial ships to extract 15,000 Americans from Lebanon when cross-border fighting flared between Lebanon-based Hezbollah and Israel.

Between 1991 and 2004, U.S. Marines evacuated U.S. citizens from conflict zones at least 10 other times, including going deep into the bush in Liberia to extract American citizens in 2003; an evacuation in Haiti in 2004; and during several post-Cold War conflicts in Africa.

U.S. diplomats, too, in the past were sometimes credited with staying on in U.S. embassies to serve U.S. citizens and seek to provide a stabilizing presence. In Liberia in 2003, for instance, then-U.S. Ambassador John Blaney stayed in Liberia's capital as mortars pounded the city, crossing front lines and meeting with warlords to successfully mediate an end to deadly fighting. It earned Blaney the State Department's highest honour, the Distinguished Service Award.

Sullivan said the U.S. "will go to great lengths to support and facilitate" the departure of Americans but also noted that the State Department has been cautioning Americans in Sudan to leave the country for years.

He added, "Americans are free people. We cannot dictate where they travel, tell them they must go or not go to a particular place."

Brig. Gen. Pat Ryder, the Pentagon press secretary, said a U.N. convoy reached Port Sudan on Monday with some evacuees.

Asked about other Americans seeking to leave Sudan, Ryder said, "Right now, to our knowledge, we're not talking about large numbers of Americans looking to come out of Sudan, but again, in the days ahead, we'll stay closely coordinated with the State Department. They're in the lead and we will be prepared to support them."

Ryder said two Navy vessels, the USS Lewis B. Puller combat ship and the USS Truxtun, a destroyer, are in the region. He said the Truxtun is off the coast of Sudan and the Puller is en route, and both will be available to help transport citizens if needed or provide medical support.

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AP writer Lolita C. Baldor contributed to this report.