Washington (CNN)Days after ordering a United States aircraft carrier out of the Middle East, the country's acting Secretary of Defense Christopher Miller has reversed that decision, instructing the USS Nimitz to remain in place due to purported Iranian threats "against President Trump and other US government officials."The USS Nimitz seen with its accompanying strike group in the Indian Ocean in July 2020. Iran appealed to the United Nations Security Council on Thursday to stop the US from conducting what it called heightened "military adventurism" in the Gulf and the Oman Sea, including dispatching nuclear-capable bombers to the region, declaring that it did not want conflict but would defend itself if necessary.According to US sources, some Iranian military forces have ramped up their readiness levels in recent days, having moved short-range ballistic missiles into Iraq, where they could potentially strike at US bases, as Iran did in the days following Soleimani's killing last year. Read MoreTrump has taken a consistently hard line on Iran, with the two countries appearing close to war around the time of Soleimani's death, though tensions had relaxed considerably during the coronavirus pandemic. With the President's time in office running out, some analysts in Washington speculate Trump could trigger a conflict with Iran to distract from his failing, baseless attempts to overturn his election loss and to complicate his successor's plans for the region."I'm genuinely concerned that the President could be thinking about saddling President-elect Biden with some kind of military operation on his way out the door," said Tom Nichols, an international affairs expert who teaches at the US Naval War College.Iran's Foreign Minister Javad Zarif himself charged Thursday that Trump is creating a pretext for war.President-elect Joe Biden wants to ease Trump's "maximum pressure" campaign against Tehran, resume engagement and return to the Iran nuclear deal, all steps that hawks in the Trump administration vehemently oppose -- and all reasons, some analysts say, that if Iran conducts any kind of attack, it would be carefully calibrated."Iran represents a real threat to US national security, particularly during this period of heightened risk due to the upcoming anniversary of the Soleimani assassination," said Sam Vinograd, a former National Security Council official and CNN analyst.However, Vinograd added, "I do think Iran will calibrate any attack associated with this anniversary because they do not want to box themselves in ahead of Biden coming into office and ostensibly restarting nuclear negotiations that would lead to the lifting of sanctions."CNN's James Griffiths contributed to this report.