The Palestinian Authority's leader condemned a "massacre".
Sixty people were killed in one day, May 14, by fire from Israeli Defence Forces at Palestinian protesters (Haaretz).
Trump, in a recorded message on Monday, said he remained committed to peace between Israel and the Palestinians.
Palestinians want East Jerusalem as the capital of their future state.
As well as calling for restraint from Israel, the United Kingdom government said peaceful protests in Gaza were "exploited by extremists".
Palestinians carry away an injured protester who was shot in his leg during clashes with Israeli forces east of Gaza City.
In the deadliest day of violence in Gaza since the 2014 war, Palestinian officials say Israeli troops have killed 55 people and wounded 2,700. Most of the wounded will be condemned to suffer lifelong injuries. "Many of them, shot hundreds of metres from the border, and many of them, children".
From withdrawing from the Paris climate accord and more recently the Iran nuclear deal to moving the United States embassy to Jerusalem, the USA and Europe no longer see eye-to-eye on key issues almost as often as they did under previous administrations.
The UK said "the large volume of live fire is extremely concerning" but said protests must be peaceful.
Kenya is among the 33 countries that sent representatives to the opening of a U.S. embassy in Jerusalem on Monday, a move that could put it at risk of more terror attacks.
Ramadan's date is dictated by the lunar calendar and was initially scheduled to begin Tuesday evening, meaning it would coincide with the annual remembrance of the Nakba, the Arabic-language term for "catastrophe" that refers to the mass displacement of Palestinians in the wake of the 1948 founding of Israel and the war with its neighboring Arab states that immediately ensued.
The Palestinians have boycotted the process since Trump's Jerusalem announcement in December.
On Monday afternoon, the White House blamed the death toll on the Palestinian Islamist group Hamas. Demonstrators gathered at several locations on the fenced enclave's border.
In a show of anger fueled by the embassy move, protesters set tires on fire, sending plumes of black smoke into the air, and hurled firebombs and stones toward Israeli troops across the border.
Israeli President Benjamin Netanyahu sought to justify the military action. "Every country has an obligation to defend its borders", he said.
Hamas has called for Israel's destruction and is in a permanent state of conflict with the Jewish state.
Administration officials have dismissed Palestinian criticism, portraying the embassy opening as an essential step toward an eventual Israeli-Palestinian peace deal.
A Foreign Office spokesperson, in a statement, said the move represents violation of worldwide law and several United Nations Security Council resolutions, in particular resolutions No. 476 and 478.
Violence broke out in the region on Monday after Donald Trump moved the American embassy in Israel from Tel Aviv to Jerusalem.
Turkey lowered flags to half-mast to mark three days of mourning for the Palestinians killed in Gaza, while China called on Israel to exercise constraint.
During the riots, Hamas' usual propaganda efforts were on full display. "This decision is not for them to make", said Egyptian lawyer, Ahmed Farag.
Eight of the dead, the army said, were armed Hamas militants in civilian clothes who tried to storm the fence in northern Gaza and attacked Israeli forces with grenades and pipe bombs before being killed in a shootout.