"The government in Cairo must improve its record protecting minority groups across Egypt, including the Coptic Christians, who make up 10 percent of the population", Cardin stated.
Trump spoke by phone Sunday with el-Sissi to express confidence that Egypt will do what it can "to protect Christians and all Egyptians".
The priest of St. George's Church in the northern Egyptian city of Tanta, where a suicide bomber killed at least 27 people, says he lost his 23-year-old son, who was among six deacons killed in the attack.
There was no immediate claim of responsibility for the attacks but Egyptian Christians have repeatedly been targeted by militants including the Daesh group.
Egypt has declared a state of emergency after two devastating suicide bombings killed more than 40 victims and injured dozens more at churches on Palm Sunday, shaking a country already struggling with political turmoil.
The worshippers had been celebrating Palm Sunday, one of the holiest days of the Christian calendar.
General view of the coffins of victims of Sunday's church attack in Tanta, Egypt, April 9, 2017.
The closure came hours before the start of the Passover holiday as did a rocket attack claimed by the Islamic State affiliate in the peninsula.
The invitation to Sisi to visit so early in Trump's administration was a very visible sign of the new course the United States has chose to take.
The December bombing in a church adjacent to the Coptic papal seat marked a shift in IS tactics.
The latest IS attacks were a blow to el-Sissi's image and left many Christians doubting whether he is capable of protecting them.
The attacks in the Nile Delta cities of Tanta and Alexandria prompted Sisi to declare a "three-month" state of emergency. "I didn't realize what's happening", he told CNN.
The attacks came just as Sisi returned from the USA where he met President Donald Trump and, to his delight, obtained a ringing endorsement of his authoritarian methods and campaign against Islamists.
He called for prayer for Pope Tawadros II, Egypt's Coptic clergy, the Coptic Orthodox faithful "who continue to be resilient in the face of ongoing and escalating attacks, and who resist the urge to react vengefully or reciprocally", and for the families, colleagues, and friends of the security services personnel that gave their lives in an attempt to foil the bomber.
Vatican City: Pope Francis will visit Egypt as planned this month despite the weekend bombings, Monsignor Angelo Becciu said, adding, "There is no doubt the Holy Father will maintain his offer to go to Egypt" on April 28 and 29. Egypt's Copts are one of the most ancient Christian communities and the largest in the Middle East, said the report. "I just want to let everybody know in case there was any doubt that we are very much behind President Sisi", Trump said.