The United States says it is not seeking conflict with Iran and that its military buildup in the Middle East aims at deterring Iranian "aggression" and protecting U.S. interests in the region.
Secretary of State Mike Pompeo made the comments on June 18 amid rising concerns about a possible military confrontation between Washington and Tehran.
The Pentagon earlier announced it would send an additional 1,000 troops to the region in response to "hostile behavior" by Iranian forces. They are to join some 1,500 additional troops deployed to the region last month.
China warned all sides "not to open a Pandora's box" and urged the United States to lower its "extreme pressure methods."
Russia also called for restraint, calling U.S. actions "rather provocative."
Iranian President Hassan Rohani said that his country "will not wage war against any nation" and had remained "loyal" to the 2015 nuclear agreement with world powers.
Relations between Washington and Tehran have grown increasing tense since the United States in May 2018 pulled out of the nuclear deal and later reimposed sanctions on Iran that had been lifted in exchange for the country agreeing to curb parts of its nuclear program.
Recent attacks on oil tankers in the Gulf of Oman and near the Strait of Hormuz have exacerbated the situation, with Washington blaming Iran for the incidents. Tehran denies any involvement.
Tensions were further fueled this week when Iran said its stockpile of low-enriched uranium, which is used to make reactor fuel and potentially nuclear weapons, would next week exceed levels set under the nuclear pact.
Speaking to reporters during a visit to U.S. Central Command in Florida, Pompeo reiterated that President Donald Trump "does not want war."
The secretary of state said the United States will "continue to work to convince the Islamic Republic of Iran that we are serious and to deter them from further aggression in the region."
He added that Washington "will continue to communicate that message while doing the things that are necessary to protect American interests in the region."
In an interview with Time magazine released earlier in the day, Trump said he was prepared to take military action to stop Tehran from having a nuclear bomb.
However, Trump left open whether he would sanction the use of force to protect oil supplies from the Persian Gulf.
He said attacks on tankers so far had been "very minor."
In a speech on state television, Rohani said that the United States -- not Iran -- was acting badly.
"Iran has been loyal to its signature," the Iranian president said. "Iran has been loyal to international agreements, and the one standing against us today is the one that has trampled all pacts, agreements, and international accords."
In Moscow, Russian Deputy Foreign Minister Sergei Ryabkov blamed Washington for implementing "a deliberate policy to instigate a war" against Iran.
Ryabkov accused Washington of being "rather provocative," with what he called "continuous attempts to increase political, psychological, economic, and military pressure" on the country.
"A large concentration of forces and hardware itself heightens the risks of collisions and some unwanted escalation," Ryabkov also warned.
China's top diplomat, State Councilor Wang Yi, warned all sides "not to take any escalatory actions that irritate regional tensions, and not to open a Pandora's box."
"In particular, the U.S. side should alter its extreme pressure methods…Any unilateral behavior has no basis in international law. Not only will it not resolve the problem, it will only create an even greater crisis," Wang added.
Trump wants to force Iran to renegotiate the 2015 nuclear accord, arguing that the terms were not tough enough to prevent Iran from developing nuclear weapons, and agree to curb its ballistic-missile program and end its "malign" activities in the Middle East.
Iran has denied it supports insurgent activity and said its nuclear program was strictly for civilian energy purposes. Iranian officials have also ruled out any negotiations on its missile program.