The US is giving Turkey "actionable intelligence" on the positions of Kurdish separatist fighters in northern Iraq, a Pentagon spokesman has said.
Geoff Morrell said intelligence would be "key for any sort of military response" to the attacks on Turkey by the Kurdistan Workers' Party (PKK).
Turkey has deployed thousands of troops on the border and threatened to invade.
Washington has been urging Ankara to show restraint in its response to the PKK, as it could destabilise Iraq.
Last week, US Defence Secretary Robert Gates said his country and Turkey needed better intelligence about the location of PKK fighters in northern Iraq before launching any military strikes.
"The key for any sort of military response from the Turks or anyone else is having actionable intelligence and that's a pretty high standard, and we are making efforts to help them get actionable intelligence."
Speaking to reporters in Washington, Mr Morrell said the US had given Turkey "intelligence with regards to this situation for a long time".
Formed in late 1970s
Launched armed struggle in 1984
Dropped independence demands in 1990s
Wants greater autonomy for Turkey's Kurds
Leader Abdullah Ocalan arrested in 1999
Ended five-year ceasefire in 2004
Called a terrorist organisation by Turkey, the EU and US
Is Turkey planning invasion?
"We are assisting the Turks in their efforts to combat the PKK by supplying them with intelligence, lots of intelligence," he added.
Following Gulf War I, George H.W. Bush promised the Kurds he would assist them in overthrowing Saddam Hussein, but the help never came and thousands of Kurds were slaughtered.