Egypt’s interim government said Wednesday that negotiations to end the nation’s political standoff have failed and that its plan to break up protests in support of ousted president Mohamed Morsi is “final.”

The declarations by the president and the prime minister raised the prospect of renewed violence between security forces and Morsi’s supporters after a flurry of high-level diplomatic visits this week failed to push the two sides toward a deal.

U.S. Deputy Secretary of State William J. Burns and Republican Sens. John McCain (Ariz.) and Lindsey O. Graham (S.C.) were among the concerned visitors to Egypt in recent days, as members of the international community sought to avert fresh clashes between Morsi’s Muslim Brotherhood backers and the interim ­military-led government.

Adly Mansour, Egypt’s interim president, said Wednesday night that the government will not extend any concessions to the Muslim Brotherhood and intends to move ahead with its political road map.

“The train of the future has left the station. It’s going forward, and all of us have to catch that train,” Mansour said in a televised address. “He who stays behind has to take responsibility for that decision.”

Earlier, the president’s office announced that international attempts to negotiate a political solution had foundered. “These efforts did not achieve the success that was hoped for, despite full support provided by the Egyptian government,” it said in a statement quoted by the state-run al-Ahram newspaper. Egypt “holds the Muslim Brotherhood fully responsible for the failure of these efforts,” it said.

Morsi’s supporters quickly dismissed the statement. “What failed was the presidency, not the negotiation efforts,” said Fathi Tamim, deputy head of the Egyptian lawyers union, which hosted a news conference Wednesday for the families of Morsi’s top aides.

The deposed president and several members of his former team, along with other prominent Islamist leaders, have been held virtually incommunicado since the military ousted Morsi in a July 3 coup. The deposed leader’s supporters have vowed to continue their protest until he is reinstated.

Tamim also warned authorities Wednesday that raiding the pro-Morsi camps would escalate the standoff into a “civil war,” a concern that was also raised by foreign dignitaries visiting this week.

A delegation of Irish and British lawmakers toured the main pro-Morsi encampment outside the Rabaa al-Adawiya mosque in Cairo’s Nasr City district Wednesday night, as protesters and their families knelt on tarps to break their final Ramadan fast. Wednesday was the last day of the Muslim month of daily fasting.

The delegates said they had met with Egypt’s foreign minister and other politicians and activists Tuesday. They said they were discouraged that neither side appeared willing to make concessions.

“No one should call timeout on negotiating in a tense situation,” said Kishwer Falkner, a member of Britain’s Parliament, adding that both the Egyptian military — which she said was still “clearly” calling the shots — and the Muslim Brotherhood appeared “inflexible.”

“I think they feel they’ve reached an impasse,” Falkner said.

On Wednesday, interim Prime Minister Hazem el-Beblawi said a government plan to clear the two sprawling pro-Morsi sit-ins that have shut down roads and neighborhoods in the capital for five weeks would soon commence.

“There is no going back,” Beblawi said in a statement published by state media. He said the only reason that security forces had not yet moved to break up the sit-ins, which include hundreds of women and children, was “out of respect for the holy month of Ramadan.”

Visiting European and American officials have called on the government to avoid a violent raid on the camps and to release Morsi and other “political prisoners” so that they can have a seat at the negotiating table. The visiting officials have also urged the Muslim Brotherhood to renounce violence.

Egyptian authorities have accused the Brotherhood of using women and children as “human shields” to keep security forces at bay.

In recent weeks, government officials have described the Brotherhood’s members as violent “terrorists” and foreign agents.

Prosecutors said this week that seven prominent Islamist leaders, including the Brotherhood’s supreme guide, would go on trial this month on charges ranging from murder to forgery. The Brotherhood says the charges are politically motivated.

Members of the European delegation also raised questions Wednesday about the charges against the Islamists. “They are clearly political prisoners,” Falkner said. “If they’re terrorists, Egypt has no shortage of terrorism laws” with which to properly try them, she said.

Wednesday night was the start of Eid al-Fitr, the holiday at the end of Ramadan when Egyptian businesses and government offices typically close for several days as families gather to rest and celebrate.

But tension and fear have clouded this year’s holiday as Morsi’s supporters insisted that their protest would continue and many other Egyptians said they back the government’s call for a crackdown.

“We have no idea what to expect,” said Sarah Attia, the wife of a top Morsi aide, Khaled al-Qazzaz, who remains in detention. “We will go down to the streets daily, regardless. And we will bring our children.”

Health officials say that more than 250 people have been killed in unrest since the coup. Security forces killed more than 80 people when they opened fire on pro-Morsi demonstrators, sparking clashes late last month, in the single deadliest attack by security forces since the 2011 uprising that ousted Hosni Mubarak.

Sharaf al-Hourani contributed to this report.