Oil prices fell to more than a one-week low on Tuesday, as investors shrugged off supply concerns and Washington and Tehran's intensifying war of words ahead of "economic D-Day."Front-month Brent crude oil futures were last seen trading 3% lower at $89.40 per barrel, its lowest since Aug. 13. U.S. West Texas Intermediate crude oil futures fell 3.2% to trade around $82.32 a barrel. Stock Chart IconStock chart iconOil pricesTuesday's moves extended declines seen on Monday, when Brent prices fell by 3%. On Tuesday morning, the New York Times reported that the U.S. State Department was preparing to return evacuated American diplomats to the Middle East as early as this week, suggesting the government is not anticipating a return to all-out warfare. While U.S. strikes in the Middle East have quieted in recent weeks, Washington has instead made moves to exert huge economic pressure on Iran.The U.S. government unveiled a fresh raft of sanctions on Iran this week, as well as so-called "enablers" that continue to trade with the country. watch nowThe White House has labeled its efforts an "economic D-Day," with Treasury Secretary Scott Bessent touting the initiative as "the single greatest financial offensive ever" on Monday. Meanwhile, U.S. Defense Secretary Pete Hegseth told reporters on Monday that the prospect of further American strikes in the Middle East remained on the table. "If we need to use kinetic strikes, we'll use them," he said. "If Iran is foolish enough to overplay their hand or mess with the American military, we'll do what we need to do.""Economic pressure hurts them the most right now," he said of the Iranian regime. "But by no means are we foreclosing using kinetic strikes anywhere in the Strait of Hormuz or around Iran."Iranian Economy Minister Ali Madanizadeh said on state television that Tehran is "fully prepared" to withstand more U.S. sanctions. "The government is and was ready and has a two-year plan to manage these events," he said. "We have our own tools and we know how to play the game."China vows to defend its interestsChina, one of Iran's largest trading partners, has repeatedly called for a diplomatic end to the U.S.-Iran war. Under the new "economic D-Day" plans, China could face ramifications for continuing to buy Iranian oil. On Tuesday, Chinese Foreign Ministry Spokesperson Lin Jian told reporters Beijing would "do everything necessary to firmly safeguard its rights and interests." "China has made clear on many occasions its firm opposition to illicit unilateral sanctions that have no basis in international law or the authorization of the UN Security Council," he said. "Economic warfare and maximum pressure provide no solution."He added that China's cooperation with Iran is conducted within the framework of international law, and should therefore not be disrupted.In a Tuesday note, BBH strategists said the Trump administration's latest tactics were "more of a warning shot than a decisive blow.""The U.S. expanded sanctions on Iran but stopped short of any immediate secondary sanctions against other countries sustaining Iran's trade. China is the critical pressure point — it is Iran's largest trading partner and buys roughly 90% of its oil exports — and the biggest constraint on making the sanctions credible."They added that targeting China as a trading partner of Iran would mean targeting major Chinese banks and refiners, "risking financial disruption, Chinese retaliation, and the fragile US-China détente."