UPDATED at 2:00 p.m.: The ultimatum posed to Egyptian President Mohammed Morsi by his own army to relinquish power or let his country fall to military rule has triggered what Morsi supporters called a “military coup,” after both sides pledged to spill blood to achieve their ends.
Representatives of the Muslim Brotherhood, allied with Morsi, tell NBC News that tanks are advancing outside Cairo, signalling a full military coup against the leadership. According to NBC, one Morsi adviser says communication with the president has been shut off and high ranking leaders have been arrested. Morsi's whereabouts are currently unknown.
As the 5 p.m. local time deadline passed, crowds chanted and waved Egyptian flags in Cairo's densely packed Tahrir Square.
Related: Photos: Morsi clashes with military as Egyptian protests escalate
In a speech televised overnight Tuesday, Morsi adamantly and passionately defended his right to rule, using the word "legitimacy" 57 times and focusing on his ascension to power through a democratic election.
"If the price of preserving legitimacy is my blood, I am prepared to pay it," Morsi said. He warned that military action to force his removal would "backfire on its perpetrators."
His critics countered on a military-affiliated Facebook page titled "Final hours:" We swear to God that we will sacrifice even our blood for Egypt and its people, to defend them against any terrorist, radical or fool."
Protests against Morsi, who was democratically elected in 2012, erupted around the one-year anniversary of his inauguration Sunday as the flash point to months of economic and political turmoil. Critics charge the embattled leader with consolidating power for his Muslim Brotherhood supporters and failing to advocate the agenda based on economic reform and inclusive government that he laid out in last year's campaign.
Related: Richard Engel reports live from Egypt
Should Morsi continue to ignore the demands of the people, the military threatened to intervene and enforce its own "road map" for the country's future. The military issued that ultimatum via state television Monday and gave Morsi 48 hours to "meet the people's demands." That deadline expired at 11 a.m. Eastern Time.
The United States has continued to press Morsi to address the demands of his people. President Obama spoke with Morsi over the phone on Monday to advise that "democracy is more than elections," White House officials said.
The U.S. will not be choosing sides on the clash, State Department Spokeswoman Jen Psaki said Wednesday. "We think that a peaceful, political resolution is the preferred option and what's best for the Egyptian people."