President Abdel Fattah al-Sisi on Thursday inaugurates a "new" Suez Canal in a lavish and heavily secured ceremony, as Egypt seeks to boost its economy and international standing, AFP reports.
But a threat by an Islamic militant group to execute a Croatian hostage kidnapped west of the capital threatened to overshadow the ceremony, showcased by authorities as proof that the country was safe.
The event in the port city of Ismailiya, due to be attended by several heads of state including French President Francois Hollande, comes two years after then army chief Sisi overthrew his Islamist predecessor.
Mohamed Morsi's ousting unleashed a deadly crackdown on Islamists, and a jihadist insurgency has killed hundreds of soldiers east of the Suez Canal.
The Islamic State group's Egyptian affiliate on Wednesday released a video threatening to execute Croatian hostage Tomislav Salopek, a worker with French geoscience company CGG, in 48 hours if female prisoners were not released.
Croatian Foreign Minister Vesna Pusic was due in Cairo on Thursday to try to secure his release.
Sisi broke ground on the canal project last August after being elected president after he promised to strengthen security and revive a dilapidated economy.
Initial estimates suggested the new route would take up to three years to build, but Sisi set an ambitious target of 12 months to finish the project.
It has been touted as a landmark achievement, rivalling the digging of the original 192-kilometre (119-mile) canal which opened in 1869 after almost a decade of work.
The new section, built at a cost of $9 billion (7.9 billion euros) and funded entirely by Egyptian investors, runs part of the way alongside the existing canal connecting the Red Sea and the Mediterranean.
"It's an achievement for the people who managed to fund it as a national project and accomplished it through perseverance and hard work," Sisi's office has said.
It involved 37 kilometres of dry digging, creating what is effectively a "second lane", and widening and deepening another 35 kilometres of the existing canal.
It will cut the waiting period for vessels from 18 hours to 11.
By 2023 the number of ships using the canal will increase to 97 per day from 49 now, the government hopes.
Officials hope the new waterway will more than double Suez earnings from $5.3 billion expected at the end of 2015 to $13.2 billion in 2023.
But analysts say the increase in ships and revenue would hinge on global trade volume and not the canal's capacity.
Sisi will open the ceremony by joining a naval parade, with some 10,000 policemen standing guard across six provinces, state media said.
Newly-acquired French Rafale warplanes and US F-16s, delivered just last week, will also be on display.
Banners saying "New Suez Canal: Egypt's Gift to the World" and hundreds of Egyptian flags graced the streets of Cairo and other cities on Thursday.
The waterway is a cornerstone for Sisi to boost his regime's legitimacy after a deadly crackdown on dissent.
In revenge, militants have killed hundreds of policemen and soldiers, mostly in the Sinai Peninsula that lies between Israel, the Gaza Strip and the Suez Canal.
Amr Adly, of the Carnegie Middle East Center, said that "since Morsi's ouster, the new regime is engaged in a political conflict to prove its legitimacy inside and outside Egypt.
"The ability to accomplish such an economic project is part of cementing this legitimacy."
The waterway is part of a comprehensive project to develop the area adjacent to the canal into an industrial hub.
"There is a stream of investors who want to invest, because the level of trust in Egypt and its political leadership is very high," Suez Canal Authority chief Mahob Mameesh said last week.
He said around one million jobs are expected to be created over the next 15 years.
Fawaz Gerges, of the London School of Economics and Political Science, called it "a magnificent project" but added that it "does not resolve the structural challenge facing the economy".