The world will be closely watching as voters in the United States, the largest economy and military power, choose their next president on Tuesday.

The immense international consequences of who becomes the next U.S. president can make it seem unfair that only U.S. citizens can vote and the rest of the world doesn't have a say.

The United States plays a key role when it comes to Ukraine, the Middle East, China, Taiwan, NATO and the trans-Atlantic alliance. For one thing, Washington – with its $916 billion military budget for 2023 – far outspends both its friends and foes.

Some of the sharpest differences between Harris, the vice president and Democratic nominee, and Trump, the former Republican president, are their policies toward Ukraine.

Harris' views on Ukraine are generally in line with those of outgoing President Joe Biden. She has committed to continued support for Ukraine, has met with Ukrainian President Volodymyr Zelenskyy many times and accused Russia of "crimes against humanity."

Ukraine war

Addressing Trump in her only debate with him, she said if he were president, "Putin would be sitting in Kyiv right now."

As a long-time critic of U.S. spending on Ukraine, Trump's comments indicate he would break with Ukrainian support. At a campaign rally in September he dubbed Zelenskyy the "greatest salesman on Earth," saying that every time he speaks with Biden, the Ukrainian leader walks away with billions in military aid.

Trump claims, without evidence, that if he were president there would not have been a war, but that if he is re-elected he could end it "in one day." He has blamed Ukraine in part for the conflict.

Trump's running mate JD Vance is even harder on Kiev. His plan to end the war calls for Russia to keep the Ukrainian territory it has conquered and prevent Ukraine from joining NATO - not dissimilar to what Russian President Vladimir Putin has demanded.

Unwavering support for Israel

It often seems that Harris and Trump are trying to outdo each other with statements about their support for Israel.

Harris, whom Trump has tried to denigrate with statements saying she "hates Israel," has come out as a strong supporter of the Jewish state.

She warned Iran, after Israel's recent retaliation against its archenemy for an Iranian attack on Israel on Oct. 1, not to escalate the conflict.

Her husband is Jewish and she is familiar with Jewish customs and culture.

In a statement following Israel's assassination of Hamas leader Yahya Sinwar, Harris said "justice has been served" but went on to call for an end to the war, a release of the hostages and for the Palestinian people to "realize their right to dignity, security, freedom and self-determination."

Harris has had to contend with an increasingly vocal left wing of her party that has demonstrated and lobbied for the U.S. to cut military aid to Israel and end the war.

Trump is generally seen as a strong supporter of the Jewish state. During his previous term, he moved the U.S. embassy from Tel Aviv to Jerusalem, to the fury of many Palestinians. But he has openly criticized Israeli Prime Minister Benjamin Netanyahu and has said Israel needs to "finish the job" of the war quickly.

For all of Trump's talk about how much he loves Israel, he has also made statements critical of Jews that some have labeled anti-Semitic.

China tariffs

When it comes to China, both candidates have focused on the economy and trade. Trump has come out with a controversial proposal to slap "beautiful" tariffs not only on China but on other economic partners – saying he will impose 10-20% tariffs on all imports and some 60% on Chinese goods.

Critics from the national security think tank, the Center for Strategic & International Studies, question whether the president has the authority to impose such tariffs but believe there "appear to be few practical or legal barriers" to Trump pushing them through.

Harris has condemned the plan, saying it would drive up prices, costing U.S. residents up to $3,900 annually.

For her part, the former senator from the high-tech state of California accuses China of stealing intellectual property.

The Biden-Harris administration subsidized some domestic high-tech production while keeping some $360 billion of the previous Trump administration tariffs and adding some of their own.

NATO concerns

Expect a Harris White House to continue policies promoted by Biden, with strong ties to European allies and NATO.

Trump, on the other hand, could reverse a lot of these policies. He has long been a critic of NATO, claiming that many European members are free-riders who don't pay their way, relying instead on U.S. taxpayers.

At a February campaign rally, he said he would "encourage" Russia "to do whatever the hell they want" to NATO countries that are not spending enough on defense.

He has flirted with taking the U.S. out of the defense alliance though the national security publication Lawfare writes that "formal exits from the alliance have been barricaded" via legal means. Still, it says a "quiet quit" whereby the U.S. disengages, is possible.

Above all, Trump is perhaps best known internationally for his "America First" agenda.

During his administration, he withdrew from the UNESCO, the UN Human Rights Council (UNHRC) and the Paris Agreement on climate change. Trump's successor Biden reversed those moves.