The Egyptian army is finding itself caught between a popular uprising, which it has vowed not to crush, and President Hosni Mubarak, from whom it has distanced itself but not abandoned, analysts say.
By dropping Mubarak, the military would endanger its position as ultimate guarantors of Egypt's security and stability, with all the economic and political trappings that come with such responsibility.
But crushing an anti-government movement that has so far received tanks and soldiers warmly would likely only erode popular respect for the military - with no guarantee it would be able to restore order.
Many have called for restraint, with the United States announcing on Monday that it will send its former ambassador to Cairo, Frank Wisner, back to the Egyptian capital as a special envoy.
"We urge you to shoulder your historic responsibility and to assist in bringing about this transition," said Human Rights Watch in an open letter to defence minister Mohammed Hussein Tantawi.
"The army has the key, said Tawfik Aclimandos, an Egypt analyst at the College de France in Paris.
"When a president decides to call upon it, the army must make the decision. The army could back Mubarak, but it doesn't want to open fire on the crowd."
The army is on the front line since Mubarak, a one-time air force general, called upon it last week to reinforce a widely despised police force unable to keep order.
Mubarak bolstered the military's clout by promoting two generals, Omar Suleiman and Ahmed Shafiq, as vice president and prime minister, respectively.
The military pledged on Monday not to fire upon protesters, acknowledging what it called "the legitimate rights of the people" without actually defining those rights.
But it held back from denouncing Mubarak, whose ouster after three decades as leader of the Arab world's most populous nation is the core demand of the uprising.
Its position may be "a sign that we might be moving towards a sort of managed transition (in which) a part of the regime would stay in place," said Elijah Zarwan from the International Crisis Group, a think tank.
The 450,000-strong military has given Egypt all its presidents - including Gamel Abdel Nasser - since the "Free Officers" coup that deposed the monarchy in 1952.
But its ranks include many young conscripts whose allegiance is uncertain and who might prove reluctant to turn their weapons on civilians.
"The Egyptian army is respected. It has no tradition of repressing popular movements," a task entrusted to the police and its riot squad, said Amr el-Shobaki from Cairo's Al-Ahram Center for Political and Strategic Studies.
Even the Islamists of the Muslim Brotherhood were split in a Monday tribute to "the glorious position of the great Egyptian army that has stood at its people's side."