WASHINGTON (AP) — President Joe Biden will deliver a rare Oval Office address Thursday night as he prepares to ask for additional billions of dollars in military assistance for Israel and Ukraine, deepening American involvement in two very different, unpredictable and bloody foreign conflicts.

The speech will be an opportunity for Biden to argue that the United States has an obligation — and a national security interest — in both places. And it's a chance for him to publicly lobby lawmakers for the money.

The funding request, expected to be formally unveiled on Friday, is likely to be around $100 billion over the next year, according to people directly familiar with the proposal who insisted on anonymity to discuss internal deliberations. The total figure includes some money for Taiwan's defense and for managing the flow of migrants at the southern border with Mexico.

Biden hopes that combining all of these issues into one piece of legislation will create the necessary political coalition for congressional approval. His speech comes the day after his high-stakes trip to Israel, where he showed solidarity with the country in its battle against Hamas and pushed for more humanitarian assistance to Palestinians in the Gaza Strip.

Ahead of his address, Biden spoke with Ukrainian President Volodymyr Zelenskyy to stress that the U.S. remained committed to backing Kyiv, the White House said. And a senior White House official said Biden continued to develop his remarks on Thursday after working with close aides throughout the week, including on his flight home from Israel. The official declined to be identified ahead of the president's speech.

Biden faces an array of steep challenges as he tries to secure the money. The House remains in chaos because the Republican majority has been unable to select a speaker to replace Rep. Kevin McCarthy, who was ousted more than two weeks ago.

In addition, conservative Republicans oppose sending more weapons to Ukraine as its battle against the Russian invasion approaches the two-year mark. Biden's previous request for funding, which included $24 billion to help with the next few months of fighting, was stripped out of budget legislation last month despite a personal plea from Ukrainian President Volodymyr Zelenskyy.

The White House has warned that time is running out to prevent Ukraine, which recently struggled to make progress in a grueling counteroffensive, from losing ground to Russia because of dwindling supplies of weapons.

There will be resistance on the other side of the political spectrum when it comes to military assistance for Israel, which has been bombarding the Gaza Strip in response to the Hamas attack on Oct. 7.

Critics have accused Israel of indiscriminately killing civilians and committing war crimes by cutting off essential supplies like food, water and fuel.

Bipartisan support for Israel has already eroded in recent years as progressive Democrats have become more outspoken in their opposition to the country's decades-long occupation of Palestinian territory, which is widely viewed as illegal by the international community.

There are rumbles of disagreement within Biden's administration as well. Josh Paul, a State Department official who oversaw the congressional liaison office dealing with foreign arms sales, resigned over U.S. policy on weapons transfers to Israel.

"I cannot work in support of a set of major policy decisions, including rushing more arms to one side of the conflict, that I believe to be short-sighted, destructive, unjust and contradictory to the very values that we publicly espouse," he wrote in a statement posted to his LinkedIn account.

Paul is believed to be the first official to have resigned in opposition to the administration's decision to step up military assistance to Israel after the Oct. 7 attack.

While visiting Tel Aviv on Wednesday, Biden told Israel that "we will not let you ever be alone." However, he cautioned Israelis against being "consumed" by rage as he said the United States was after the Sept. 11 attacks of 2001.

Wartime decision-making, Biden said, "requires asking very hard questions" and "clarity about the objectives and an honest assessment about whether the path you are on will achieve those objectives."

A speech from the Oval Office is one of the most prestigious platforms that a president can command, an opportunity to try to seize the country's attention at a moment of crisis. ABC, NBC and CBS all said they would break into regular programming to carry the address live.

Biden has delivered only one other such speech during his presidency, after Congress passed bipartisan budget legislation to avert a default on the country's debt.

The White House and other senior administration officials, including Office of Management and Budget Director Shalanda Young, have quietly briefed key lawmakers in recent days about the contours of the planned supplemental funding request.

The White House plans to formally unveil Biden's supplemental request on Friday, according to two officials familiar with the plans, although the timing could change.

The Senate plans to move quickly on Biden's request, hoping that it creates pressure on the Republican-controlled House to resolve its leadership drama and return to legislating.

Border security will likely be a contentious issue in spending conversations.

Although there was a lull in migrant arrivals to the U.S. after the start of new asylum restrictions in May, illegal crossings topped a daily average of more than 8,000 last month.

"There's a huge need to reimburse for the costs of processing," said Sen. Chris Murphy, D-Conn., who leads a Senate panel that oversees funding for the Department of Homeland Security. "So it's personnel costs, it's soft-sided facilities, it's transportation costs."

Biden's decision to include funding for Taiwan in his proposal is a nod toward the potential for another international conflict. China wants to reunify the self-governing island with the mainland, a goal that could be carried out through force.

Although wars in Europe and the Middle East have been the most immediate concerns for U.S. foreign policy, Biden views Asia as the key arena in the struggle for global influence.

The administration's national security strategy, released last year, describes China as "America's most consequential geopolitical challenge."

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Associated Press writers Matthew Lee and Mary Clare Jalonick and AP media writer David Bauder contributed to this report.