U.S. President Joe Biden will look to burnish his foreign policy legacy in a U.N. speech on Tuesday, still facing challenges posed by Ukraine's effort to repel Russian invaders and a Middle East mired in war.

With four months left in office, Biden will step up to the green-marbled lectern to address world leaders at the U.N. General Assembly, where wars in both regions pose dilemmas likely to outlast his presidency.

As efforts falter to impose a Gaza truce and with Israel and Lebanon's Hezbollah waging a cross-border battle, the Pentagon said on Monday it will send a small number of additional troops to the Middle East out of an abundance of caution.

Biden's presidency has been dominated by foreign policy challenges, from Russia's February 2022 invasion of Ukraine to the Palestinian Hamas attack in southern Israel and hostage-taking on Oct. 7, and the resulting Israeli assault on Gaza.

Countering China and Iran, which backs both Hamas and Hezbollah, has consumed significant portions of the president's time.

A senior administration official said Biden's speech at 10 a.m. EDT (1400 GMT) will give him an opportunity to highlight what he considers major achievements of his time in office and to emphasize that the international community should support Ukraine and pursue a diplomatic solution in the Middle East.

White House press secretary Karine Jean-Pierre told reporters on the Air Force One flight to New York that Biden will outline his "vision for how the world should come together to resolve these big problems and defend fundamental principles such as the U.N. Charter."

Biden is scheduled to hear from Ukrainian President Volodymyr Zelenskyy about a new Ukrainian peace plan when they meet in Washington on Thursday. A U.S. official said the plan is likely similar to previous plans calling for increased weaponry and support for Ukraine's fight.

"We support Ukraine's pursuit of a just, lasting, and comprehensive peace to this war. And the president is committed to providing the Ukrainian military with the equipment they need to strengthen their position," Jean-Pierre said.

Biden's U.N. speech will be the centerpiece event of a two-day visit to New York that includes a climate speech later on Tuesday and a meeting on Wednesday with To Lam, the president of Vietnam.