With tanks and barbed wire ringing the presidential palace, Egyptian President Mohamed Morsi on Thursday called for a “national dialogue” but remained determined to press forward with a controversial referendum on an Islamist-backed constitution that has plunged this nation into a political crisis.

In a televised speech, Morsi called Wednesday night’s clashes between his Islamist backers and liberal, secular and other opponents the work of “infiltrators” inside the opposition. He said some protesters had been paid and armed to perpetrate “thuggery” and “terrorism,” harsh rhetoric that is sure to rally his Muslim Brotherhood supporters and inflame opponents, who see Egypt’s first democratically elected president as an Islamist dictator in the making.

But if Morsi appeared emboldened, it may have had less to do with his support from the Muslim Brotherhood than with his newfound friendship with Egypt’s vaunted, wealthy, U.S.-supplied military, which deployed tanks and armored trucks in defense of the presidential palace early Thursday.

That pointed display by the Republican Guard — a discrete military unit charged with protecting the palace — followed a night of clashes that left seven people dead and more than 700 wounded. And it reflected a closeness between Morsi and the military sealed for now by the draft constitution, which he is so insistently advocating and which enshrines the military’s vast powers and autonomy to an unprecedented degree.

In a telephone call to Morsi later Thursday, President Obama expressed “deep concern’’ about the deaths and injuries of protesters and said that “all political leaders in Egypt should make clear to their supporters that violence is unacceptable,” the White House said.

The relatively small show of force by Egypt’s military — seven tanks, 10 armored trucks and a few dozen soldiers who set out coils of barbed wire — followed a meeting early Thursday that included Morsi; his newly appointed, young and openly Islamist defense minister, Abdul Fatah Khalil al-Sisi; Gen. Hamid Zaki, the newly appointed head of the Republican Guard, considered a Morsi loyalist; and other officials, a spokesman said.

Although the move Thursday by the Republican Guard by no means indicates that Morsi has deep or widespread support in the military, which is as divided and complex as Egypt itself, it suggested that the army remains the ultimate arbiter of power in post-revolutionary Egypt, just as it has been for decades. And it marked another political rearrangement in a turbulent transition that has seen many of them — in this case, a turnaround in the relationship between the two most powerful institutions in the country, after decades in which Morsi’s Muslim Brotherhood supporters were repressed with the backing of the military.

Although some observers cautioned against reading too much into Thursday’s tank deployments, other analysts considered it a significant moment for Morsi.

“The most plausible interpretation is indeed that al-Sisi and the incumbent high command are standing firmly by Morsi and the Muslim Brotherhood,” said Robert Springborg, an expert on the Egyptian army at the Naval Postgraduate School in Monterey, Calif. “They chose essentially to stand with him, clearing the area of protesters.”

The Republican Guard’s move came as some protesters were calling on the military — considered a hero during the revolution that ousted autocrat Hosni Mubarak about two years ago — to side with them in opposing a Nov. 22 decree by Morsi that grants him near-absolute powers until the draft constitution is adopted. By Thursday afternoon, at least six of his advisers had resigned over the decree, and Egypt’s influential al-Azhar University, a seat of moderate Islam, was calling on Morsi to rescind it.

In his telephone call to Morsi, Obama welcomed the Egyptian president’s call for a dialogue Saturday with the opposition “but stressed that such a dialogue should occur without preconditions,” the White House said.

According to a senior administration official in Washington, Morsi’s relationship with the military seems solid. “We have not seen any cracks,” said the official, who was not authorized to speak on the record.

Winning military’s trust

Morsi seems to have won the military’s loyalties after an Islamist-dominated constitution-writing panel approved a draft charter that enshrines the armed forces’ sweeping powers to a degree not seen even during Mubarak’s rule.

According to analysts who have studied it, the centerpiece of the charter is the creation of a 15-member national defense council — including eight military appointees — that is essentially an autonomous overseer of military affairs.

Critically, the council has the power to approve declarations of war, a provision that analysts cast as a kind of safety valve for the United States, which remains wary of an Islamist government with ties to the Palestinian militant group Hamas that might jeopardize the 1979 peace treaty between Egypt and Israel.

The council would handle military trials, which also are allowed for Egyptian civilians who are deemed a threat to the military. Although parliament must approve the overall budget figure, the council would handle all of its details, which are not required to be made public.

And in a provision that challenges any pretense of civilian oversight of the military, the draft charter requires that the president appoint the defense minister from among the ranks of the military.

“I think the military could not have asked for a better outcome” in a draft charter, said Tom Ginsburg, a professor at the University of Chicago Law School who focuses on comparative and international law. “It is hard to imagine a civilian-drafted document giving them any more autonomy.”

Viewed through the lens of the draft constitution that codifies such extraordinary powers to the military, Springborg said, Egypt’s political crisis appears to be a battle over the leftover crumbs, one in which Morsi will continue to have the upper hand.

“The real struggle for power in Egypt has to do with the military,” he said. “And as long as the Muslim Brotherhood is protecting that in exchange for the military defending it, you will get no progress. And Egypt will continue to be a military state.”

Retired Gen. Sameh Saif el-Yazl, a military analyst, called the relationship between Morsi and the military “just super.”

“And in the last few weeks, it is still improving.”

Troops vs. protesters

But the same cannot be said for relations between protesters and the security forces sent to protect the presidential palace Thursday.

“Who are you protecting?” a man shouted at soldiers through the barbed wire Thursday afternoon.

“You!” a commander yelled back.

“How are you protecting us? Where were you yesterday when they were hitting us?” the man screamed.

“You’re doing a good job,” shouted Mohamed Adel, a cashier, over the heckler. “Everyone needs to calm down.”

Ingy Hassieb and Sharaf al-Hourani in Cairo and Karen DeYoung in Washington contributed to this report.