Pentagon Press Secretary John Kirby rejected on Tuesday reports that the US had carried out a drone strike targeting hardline Islamist militants on the Iraq-Syria border.
BBC Arabic reported earlier on Tuesday that unmanned American aircraft had bombed the area of al-Qaim, which was overrun over the weekend by Sunni fighters led by the Islamic State in Iraq and Syria (ISIS).
Kirby said there was "no truth to rumors in media" of such reports.
The BBC report, citing sources close to Iraqi Prime Minister Nuri al-Maliki, emerged as US Secretary of State John Kerry held crisis talks with leaders of Iraq's autonomous Kurdish region on Tuesday urging them to stand with Baghdad in the face of a Sunni insurgent onslaught that threatens to dismember the country.
US President Barack Obama has held off granting a request for air strikes from Iraq's Shi'ite-led government but last Thursday offered up to 300 Americans to help contain a lightning offensive by Sunni insurgents, amid an unfolding humanitarian crisis with hundreds of thousands displaced.
Speaking after a meeting with his national security team, Obama said he was prepared to take "targeted" military action later if deemed necessary, thus delaying but still keeping open the prospect of airstrikes to fend off a militant insurgency. But he insisted that US troops would not return to combat in Iraq.
Obama also delivered a stern message to al-Maliki on the need to take urgent steps to heal Iraq's sectarian rift, something US officials say the Shi'ite leader has failed to do and which the al-Qaida splinter group ISIS, leading the Sunni revolt, has exploited.
Obama, who withdrew US troops from Iraq at the end of 2011, said the United States would increase support for Iraq's beleaguered security forces. But he stopped short of acceding to Baghdad's request for the immediate use of US air power against Islamist insurgents who have overrun northern Iraq.
Reuters contributed to this report.