Gaza City, Gaza Strip - Israel's military warned Gaza residents on Monday that it would stop any breach of its border fence and that those approaching it in a planned mass protest would be putting their lives in danger.
Gaza's Hamas rulers have said tens of thousands are expected to head to the border Monday and raised the possibility of large crowds breaking through the fence.
With Israel and Hamas digging in, there has been growing concern about large numbers of casualties.
Monday's march is part of a weekslong campaign, led by Hamas and fueled by despair among Gaza's 2 million people, to break the decade-old border blockade of the territory by Israel and Egypt.
Since weekly border marches began in late March, 42 Palestinian protesters have been killed and more than 1 800 wounded by Israeli army fire.
Leaflets dropped over Gaza by army jets warned that those approaching the border "jeopardize" their lives. The warning said the army is "prepared to face all scenarios and will act against every attempt to damage the security fence or harm IDF soldiers or Israeli civilians."
Monday's protest also targets the inauguration of a US Embassy in contested Jerusalem later that day.
President Donald Trump announced his decision in December to recognize Jerusalem as Israel's capital, triggering a joyous reaction from Israeli Prime Minister Benjamin Netanyahu's nationalist government. The move infuriated the Palestinians, who seek to establish a future capital in Israeli-annexed east Jerusalem.
Palestinian President Mahmoud Abbas cut ties with the Trump administration and declared it unfit to remain in its role as the sole mediator in peace talks.
Saeb Erekat, a senior Abbas aide, blasted the Trump administration Monday, saying Trump had violated a promise to hold off on moving the embassy to give peace talks a chance and that his administration is "based on lies."
Erekat said the Trump administration has "become part of the problem, not part of the solution." He suggested Trump's Mideast team is unqualified, saying "the world needs real leaders, and those (White House officials) are real estate dealers, not leaders."
Administration officials have dismissed Palestinian criticism, portraying the embassy opening as an essential step toward an eventual Israeli-Palestinian peace deal.
Trump's Mideast peace negotiator, Jason Greenblatt, wrote on Twitter that "the long-overdue step of moving our Embassy is not a departure from our strong commitment to facilitating a lasting peace deal."
Greenblatt and other administration officials have not said how they would move forward without a Palestinian partner.
Netanyahu praised Trump's "bold decision" in upending decades of U.S. policy by recognizing Jerusalem as Israel's capital. "It's the right thing to do," a smiling Netanyahu told the jubilant crowd at a reception in Jerusalem late Sunday.
Although Trump has said his declaration does not set the final borders of the city, his recognition of Jerusalem as Israel's capital has been perceived by both Israel and the Palestinians as taking Israel's side in the most sensitive issue in their conflict. Only two countries, Guatemala and Paraguay, have said they will follow suit. Most of the world maintain embassies in Tel Aviv, saying the Jerusalem issue must first be resolved.
In a reflection of the deep sensitivities, dozens of countries - including Britain, France and Germany - skipped a celebration Sunday night at the Israeli Foreign Ministry.
Monday's opening will be attended by Trump's daughter Ivanka and son-in-law Jared Kushner, who both serve as White House advisers. Kushner leads the Trump Mideast team.