Former Vice President Joe Biden's voted in favor of the 2003 invasion of Iraq, which began 16 years ago on Wednesday.

In the months leading up to the start of the conflict, Biden cited former Secretary of State Henry Kissinger to defend his stance, and contended the US invasion was not preemptive.

Biden is expected to run for president in 2020, and could face questions about his foreign policy record on the campaign trail.

Former Vice President Joe Biden's vote in favor of the 2003 invasion of Iraq, which began 16 years ago today, could cause the long-rumored presidential candidate problems during the 2020 Democratic primaries.

Biden, a US senator for Delaware at the time, defended the conflict as not preemptive in nature and made the case for the war in speeches.

"I will vote for the Lieberman-Warner amendment to authorize the use of military force against Iraq," Biden said in October 2002. "I do not believe this is a rush to war. I believe it is a march to peace and security."

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In the speech Biden also invoked for Secretary of State Henry Kissinger, who has been heavily criticized by many on the political left:

"As the most powerful nation in the world, the United States has a special unilateral capacity and indeed obligation to lead in implementing its convictions. But it also has a special obligation to justify its actions by principles that transcend the assertions of preponderant power. It cannot be in either the American national interest or the world's interest to develop principles that grant every nation an unfettered right of preemption against its own definition of threats to its security."

"Dr. Kissinger is right," Biden added. "What message would declaring a policy of prevention send to the Indians and Pakistanis, the Chinese and the Taiwanese, the Israelis and the Arabs, the Russians and Georgians?"

The 2003 Iraq War was met with pushback from many parts of the international community, who said the US was launching a unilateral, preemptive invasion without the support of the UN. In 2004, then-UN secretary general Kofi Annan condemned the conflict as illegal.

In the run-up to the conflict, Biden argued that the invasion would not be preemptive.

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"If we go to war with our partners to disarm Saddam, it will be to enforce the UN resolutions, which I would argue in terms of international law are the equivalent of a peace agreement," Biden said in February 2003. "This is not — is not — preemption. There's nothing preemptive about it. If you turned on now and the television showed aircraft striking Baghdad, it would not be a preemptive attack. There is nothing preemptive about it. It's an enforcement."

RELATED: Saddam Hussein's life

18 PHOTOS Saddam Hussein's life See Gallery Saddam Hussein's life TIKRIT, IRAQ: Photo dated 1960 of Iraqi President Saddam Hussein in his hometown of Tikrit. Saddam came to power in 1979. (Photo credit should read AFP/Getty Images) Baghdad, IRAQ: (FILES): This black and white reproduction of a picture taken in 1960 shows Saddam Hussein as a young member of the Baath Party. Ousted Iraqi leader Saddam Hussein was executed by hanging early Saturday morning, 30 December 2006, state-run Iraqiya television reported. AFP PHOTO/FILES (Photo credit should read -/AFP/Getty Images) French Prime minister Jacques Chirac (R) confers 03 March 1975 in Hotel Matignon in Paris with Iraqi Vice-President Saddam Hussein. As Premier, Chirac welcomed Saddam Hussein to France, referring to him as 'a personal friend'. France became Iraq's main military supplier in the West and was building a nuclear reactor for Iraq that was destroyed by the Israelis in 1979. AFP PHOTO / AFP (Photo credit should read /AFP/Getty Images) UNSPECIFIED - JANUARY 01: The Iraki President Saddam Hussein (Photo by Keystone-France/Gamma-Keystone via Getty Images) HAVANA - JANUARY 30: Iraqi vice-president Saddam Hussein (C), stands with Cuban President Fidel Castro (L) and Defense minister General Raul Castro (R), 30 January 1979 in Havana, during his visit to Cuba. (Photo by AFP/Getty Images) circa 1985: Iraqi president Saddam Hussein. (Photo by Hulton Archive/Getty Images) Iraqi President Saddam Hussein 10 November 1987 in Amman during a session of the emergency Arab summit. Saddam took the number two job under president Ahamd Hassan al-Bakr, began purging the army of non-Baathist officers, ridding the political scene of Kurds and communists. When Bakr stepped down, officially for health reasons, the stage was set for Saddam, who became president on 16 July 1979. Fearing the impact of Tehran's Islamic revolution on Iraq's majority Shiite Moslem population, Saddam launched a war against Iran in 1980 to defend 'the eastern flank of the Arab nation from the Persian. But he only managed to obtain a cease-fire in 1988. On 02 August 1990, Saddam directed his army against Kuwait. In February 1991 a multinational coalition led by the United States chased Iraqi troops out of he emirate. (Photo credit should read MONA SHARAF/AFP/Getty Images) This photo taken from Iraqi TV shows Iraqi President Saddam Hussein (L) patting Stuart Lockwood, 6, a young British boy on the head 23 August 1990 in Baghdad during an Iraqi TV broadcast. Saddam, flanked by army officers and an interpreter, appeared on the world's television screens in an attempt to allay fears about the treatment of Western hostages held in Iraq. Hundreds of Britons and Americans have been brought from Kuwait to be detained in Baghdad. Iraq's army has invaded 02 August its oil-rich neighbour, Kuwait. AFP PHOTO (Photo credit should read -/AFP/Getty Images) Portrait of Saddam Hussein (Photo by Leopold Nekula/Sygma via Getty Images) Iraqi President Saddam Hussein addresses the nation January 17, on the occasion of the ninth anniversary of the Gulf War. [Saddam, in a televised address to the nation, praised the "mother of all battles" and insisted that Iraqis emerged victorious in the six-week war with U.S.-led multinational forces that began on January 17 1991]. (QUALITY FROM SOURCE) BAGDAD, IRAQ - OCTOBER 18: Iraqi President Saddam Hussein waves to his supporters in his first public appearance in Baghdad 18 October since he was reelected as President for seven years in a referendum with 99.96 percent of the votes. AFP PHOTO (Photo credit should read INA/AFP/Getty Images) BAGHDAD, IRAQ: Iraqi president Saddam Hussein, wearing a white hat, swims in the Tigris river in Salahuddin area, near his birthplace in the Tikrit 16 September 1997. The Iraqi news agency said Saddam swam across 'the immortal Tigris' river three times to encourage participants in a swimming national tournament. The man with him is unidentified. (Photo credit should read STR/AFP/Getty Images) - PHOTO TAKEN 12MAY1999 - Former Iraqi president Saddam Hussein (R) is decorated with a medal presented to him by his deputy Izzat Ibrahim in Baghdad in this May 12, 1999 file photo. Ibrahim, the most senior member of the former regime, has died, [Al Arabiya satellite television quoted a Baath party statement as saying on Friday.] He is number six on the U.S. military's list of the 55 most-wanted Iraqis, with a $10 million reward offered for his capture. Iraqi President Saddam Hussein fires shots into the air on December 31, 2000. Saddam presided on Sunday over what appeared to be the biggest military parade in Baghdad since the 1991 Gulf War, greeting army units with shots from a rifle he held in one hand. REUTERS/Faleh Kheiber FR05090005 PP03040084 Iraqi President Saddam Hussein addresses the nation August 8, 2001 to commemorate the 13th anniversary of the ending of the Iraq-Iran war. The Iran-Iraq war lasted almost eight years, from September 1980 until August 1988, when Iran accepted a UN security council resolution, leading to an August 20, 1988 ceasefire. The speech comes amid widespread speculations that the U.S. might launch fresh military attacks against Iraq, who remains defiant after 11 years of economic sanctions and the U.S. military pressure. fk/AA IRAQ - DECEMBER 13: This unsourced picture alleges to show Iraqi leader Saddam Hussein in an unknown location in Iraq after his capture by US troops on December 13, 2003 from an underground hole on a farm in the village of ad-Dawr, near his hometown of Tikrit in northern Iraq. The unauthorized images, from a series of images of the deposed dictator, have allegedly not been cleared for release by the US army but have been in open circulation on the internet. (Photo by Getty Images) Saddam Hussein addresses the court during the resumption of his trial in Baghdad December 21, 2005. Saddam told his trial on Wednesday he was beaten in [U.S. custody and, in an extraordinary outburst towards the end of the hearing, also said those who had tortured Iraqis should be punished for their crimes]. ? QUALITY DOCUMENT BAGHDAD, IRAQ - UNDATED: In this composite image of sixteen photographs, former Iraqi President Saddam Hussein is seen in court during his trial, in the fortified 'green zone' in Baghdad, Iraq. Hussein was found of guilty over his role in the killing of 148 people in the mainly Shia town of Dujail in 1982 and sentenced to death by hanging, along with 2 co-defendants. After his appeal against his death sentence was rejected, speculation has become rife over when the death sentence will be carried out. (Photo by Pool/Getty Images) Up Next See Gallery Discover More Like This HIDE CAPTION SHOW CAPTION of SEE ALL BACK TO SLIDE

More recently, Biden has been teasing a possible 2020 presidential run. If he declares, Biden will likely face questions on his long record in Washington, which could include scrutiny of his defense of the Iraq invasion.

Many of the liberal voters who will decide the Democratic primary are staunchly anti-war and anti-intervention, hence the growing popularity of candidates like Sen. Bernie Sanders — who voted against the invasion.

The issue already came up in 2016, when former Secretary of State Hillary Clinton faced significant criticism over the fact she voted for the Iraq invasion while a US senator for New York. Overall, 29 Democratic senators voted in favor of authorizing the use of military force in Iraq

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Biden hasn't even announced yet, but has already seen his record on race relations dissected at a time when Democrats seem to crave diverse, progressive candidates. Biden's support for one of the most divisive conflicts in the modern era will likely be no exception to this trend of scrutiny. With that said, Biden has been at the top of recent polls, even though he hasn't officially joined the race.

The US justified the invasion of Iraq by citing what ultimately proved to be false intelligence that Hussein had weapons of mass destruction.

Biden in 2005 expressed regret about voting in favor of the invasion.

"It was a mistake," Biden said on NBC's Meet the Press at the time. "It was a mistake to assume the president would use the authority we gave him properly...We gave the president the authority to unite the world to isolate Saddam. And the fact of the matter is, we went too soon. We went without sufficient force, and we went without a plan."

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