Israeli Prime Minister Benjamin Netanyahu speaks before the U.S. Congress on Wednesday, with some Democratic lawmakers boycotting the appearance, and continuing protests expected in Washington over his hardline government's stance on the war in Gaza.

Netanyahu is assured a warm welcome from Republican lawmakers who arranged his speech in the House chamber, an appearance making him the first foreign leader to address a joint meeting of Congress four times, surpassing Winston Churchill.

Many Democrats and political independent Bernie Sanders plan to boycott Netanyahu's appearance. Vice-President Kamala Harris, who serves as president of the Senate and traditionally would sit behind whatever dignitary is speaking, says a long-scheduled trip will keep her away Wednesday. And the next Democrat in line, Sen. Patty Murray of Washington, is declining to attend.

Republicans targeted the absence of Harris, the new Democratic front-runner for the presidency, as a sign of disloyalty to an ally. However, Republican nominee Donald Trump's running mate, J.D. Vance, said campaigning would also make him a no-show for the Israeli leader's speech.

WATCH l Israel-U.S. expert Aaron David Miller on the political stakes of the speech:

Israel PM Netanyahu visits Washington amid Gaza assault, changing U.S. politics | Canada Tonight

Amid Israel’s brutal assault on the Gaza Strip and a changing political landscape in the U.S., Israel Prime Minister Benjamin Netanyahu has flown to Washington for a controversial speech at a joint meeting of Congress. Aaron David Miller, a senior fellow at the Carnegie Endowment for International Peace, discusses Netanyahu’s Washington visit.

And outside the Capitol, demonstrators angry over the deaths of nearly 40,000 Palestinians, or over Netanyahu's inability to free Israeli and American hostages taken by Hamas and other militants in the first hours of the Israel-Hamas war, are promising massive protests.

The United States is Israel's most important ally, arms supplier and source of military aid as Israel battles to break Hamas since the group considered a terrorist organization by several Western countries led attacks on Israel on Oct. 7.

Netanyahu's visit is his first abroad since the war started.

Ceasefire hopes linger

President Joe Biden's administration says it wants to see Netanyahu focus during his visit on helping it complete a deal for a ceasefire and hostage release in the nine-month war. The hard-right wing of Netanyahu's coalition has disdained the possibility of a pause in fighting.

"Once the Knesset goes out of session July 28th, Mr. Netanyahu no longer has to worry about a no-confidence motion, and if he's going to move, and if Hamas is going to move, it's going to occur in mid-August," Aaron David Miller, the former Middle East negotiator who's now a senior fellow at the Carnegie Endowment for International Peace, told CBC News this week.

Netanyahu says his aims for the U.S. visit are to press for freeing hostages held by Hamas, to build support for continuing Israel's battle against the group, and to argue for continuing to confront Hezbollah in Lebanon and other Iranian-allied groups in the region.

Republican House Speaker Mike Johnson arranged the address before the recent American political turmoil, which has included the assassination attempt against Trump and Biden's decision not to seek a second presidential term.

"I don't know all the motivations for Speaker Johnson initiating the invitation but clearly he wanted to throw a political lifeline to Netanyahu, whose popularity is very low in Israel right now," Sen. Chris Van Hollen, among the dozens of Democrats set to boycott, said Tuesday.

Vermont Sen. Bernie Sanders, who is Jewish, was more incendiary, characterizing the joint address as "the first time in American history that a war criminal has been given that honour." The chief prosecutor for the International Criminal Court has applied for arrest warrants for Netanyahu, and specific Israeli and Hamas officials for charges including war crimes.

Speech in Obama's term roiled Democrats

Some veteran Democrats are wary about Netanyahu after he used a 2015 joint address to Congress to denounce then-president Barack Obama's pending nuclear deal with Iran, but many members of the party are attending. That includes Senate Majority Leader Chuck Schumer of New York, who called for new elections in Israel in a March floor speech and called Netanyahu an obstacle to peace in the region.

In addition to multiple protests planned in and around the Capitol, relatives of Israeli hostages are planning a vigil on the National Mall.

The Health Ministry in Gaza says over 39,100 Palestinians have been killed in the war, with its total not distinguishing between fighters and civilians. The attacks led by Hamas on Oct. 7 resulted in about 250 people being taken hostage and about 1,200 killed, according to Israeli government tallies.

WATCH l Dozens killed in Khan Younis strike in Gaza:

Strikes in Eastern Khan Younis force Palestinians to flee their homes

After they ordered civilians evacuate the area, the Israel Defence Force targeted an area east of Khan Younis which left at least 37 dead and 120 injured from numbers from officials in Gaza

It is believed by the Israeli government that 116 hostages have yet to be repatriated, though about one-third have so far been pronounced dead in absentia. Several hostages unaccounted for are American citizens.

After the address, Netanyahu plans to meet with Biden and Harris on Thursday, and Trump at his Mar-a-Lago residence in Florida on Friday.