Hours after the Assad dictatorship fell in Syria, business owner Rasin Katta got a call from a former business partner in Damascus.

“‘Rasin, we’re going to start working again,’” Mr. Katta recalled the partner telling him excitedly. “‘We can start preparing the factory.’”

Mr. Katta, whose family owned medical and pharmaceutical businesses, had left Syria for Germany during the nearly 14-year Syrian civil war. And he, too, was hopeful.

With President Bashar al-Assad gone, Mr. Katta had expected the United States and other Western countries to immediately lift economic sanctions on Syria, many of them targeting the Assad regime. But months passed and that did not happen.

Instead, the Trump administration set conditions to remove the sanctions, and the hopes of Mr. Katta and other business ownerswere dashed. On Tuesday night, their optimism was renewed, when President Trump announced during his visit to Saudi Arabia that the United States would end the Syria sanctions.

“We can move forward,” Mr. Katta said after hearing the news. “We can start planning.”

U.S. sanctions on Syria date back to the 1970s, when Washington declared the country a state sponsor of terrorism. Additional sanctions were imposed over the past 14 years in response to the Assad regime’s brutal crackdown on his own people during an anti-government uprising that began in 2011.

The sanctions were intended to isolate and put pressure on the dictatorship, but it remained entrenched.

Some Western governments, including Britain and the European Union, eased the restrictions soon after the Syria’s transitional government took power.

But the Trump administration demanded a number of conditions: It wanted assurances that Iran, a close ally of the former Assad regime, and its proxies would not be operating on Syrian territory. It pressed for the destruction of the country’s chemical weapons stock and the exclusion of foreign fighters from official roles in the new government, as well as measures to protect the security and freedoms of ethnic and religious minorities and assistance in the recovery of American citizens who had disappeared in Syria.

Mr. Trump met with the new Syrian president on Wednesday in Saudi Arabia and urged the Syrian leadership to make further efforts to meet many of those conditions.

But he did not address when sanctions would be lifted and by what mechanism. And while the president has the power to lift some restrictions, Congress would need to remove others.

Some Syrian businessmen said they are worried that the removal of sanctions could get bogged down in U.S. politics.

Nevertheless, Syrian business and factory owners and traders who left the country during the civil war are already drawing up plans to return to the country and take part in rebuilding.

More than 90 percent of the population lives in poverty, and one out of every four people is unemployed, according to the United Nations. The value of the Syrian currency plummeted during the civil war years, adding to the misery.

Some governments and private investors are looking to help.

Saudi Arabia and Qatar have said they would jointly repay Syria’s $15 million debt to the World Bank, potentially unlocking millions in aid. International investors have been visiting Syria for months but have been reluctant to begin any projects because of sanctions.

As long as the U.S. sanctions remain in place, Syrian businesses cannot use Swift, a service that connects thousands of financial institutions worldwide and enables cross-border money flows. That means importers, exporters and banks would need to find different ways to transmit payments, such as the black market or hawala systems, an unofficial money transfer network.

Rami Sharrack, a 49-year-old Syrian business consultant, recently traveled to the capital, Damascus, to meet with businesspeople as well as the chambers of commerce and trade. All agreed there were huge economic opportunities in postwar Syria, but few were willing to take risks if Western sanctions remained.

On Tuesday, he said he was already getting calls from business owners and investors interested in coming to Syria.

“Lifting the sanctions will have an immediate affect,” said Mr. Sharrack, the founder of TATWIR, a consulting firm that advises Syrian private sector businesses. “And it will give a green light to countries that they can resume helping to reconstruct Syria.”

Mr. Katta said he fled Syria in 2012, a year into the civil war, and in the following years, he and his family closed their businesses back home. A pharmaceutical factory in Damascus is still standing, but the building has been looted and even the roof was stolen for scrap metal. He is planning to eventually return to Syria, but not just yet.

At the beginning of the war, Afif AboDan, 50, said he moved Typik Foods, his food and beverages business, to neighboring Turkey, where millions of Syrians fled during the conflict. He shuttered his aluminum factory.

Weeks after Mr. al-Assad’s ouster, he returned to Syria from Canada, where he lives, for what he called an “exploratory visit.” He is planning another visit this summer, to look for a location for a factory and apply for a business license.

“We are so happy at this news,” he said on Tuesday night. “Me and others now have to think seriously to return to Syria. We are very optimistic.”

Mr. AboDan said he could employ about 200 people once he reopens the company. Thousands of new jobs would be created if others like him were also allowed to restart operations in Syria, he added.

“It could help solve the crisis in the country,” he said. “When the economy returns, the security in the country improves. There isn’t security in part because people don’t have jobs and there is lots of poverty.”

Syrians speak often of the connections between economic recovery, security and the return home of the millions who sought refuge abroad during the civil war. The economy won’t improve without sanctions being lifted, they say. Security won’t improve without economic recovery. And Syrians won’t return if security doesn’t improve.

For Hassan Tarabishi, 57, who owns water treatment and pharmaceutical companies, returning to Syria from the United Arab Emirates is about more than just helping the economy. It is about having a stake in the country’s political transition at a time of great change.

“We will not lose our country again,” he said recently, speaking from his company’s former headquarters in Damascus, which was last used in 2014. The building has no electricity, and his disused office, with shelves of dusty files and sample medications, was lit only by a single battery-powered light.

“It’s important for all Syrians who have gained experience abroad in free countries to return,” he said.

On the cover of his laptop is a sticker featuring Syria’s new green flag. Mr. Tarabishi said he sees it as his patriotic duty to help rebuild the country.

“We want Syria to be a stable country with peace and prosperity,” he said. Lifting the sanctions “is a first step toward that.”