U.S. officials are looking at imposing sanctions against Russia and China for cyberattacks on the government’s servers.

The officials, who spoke to Reuters on the condition of anonymity, said no final decision has been made because the sanctions could cause strain in relations between the countries.  The Chinese president is scheduled to visit the U.S. this month.

Chinese and Russian hackers have accessed secure databases to steal information about military members and intelligence personnel and Russian hackers monitored the emails of state department officials for several months last fall.

Chinese hackers are believed to have caused the breach at the Office of Personnel Management (OPM) earlier this year.

“Frustration has been growing for years about cyber economic espionage and then the scale of the OPM attack was the straw that broke the camel’s back,” said a former senior administration official.

Chinese officials responded to the anonymous claims by saying they are firmly against cybercrime.

“The Chinese government staunchly upholds cyber security, firmly opposes and combats all forms of cyber attacks in accordance with law,” Chinese Embassy spokesman Zhu Haiquan said in a statement.

Zhu added he doesn’t want U.S. officials to engage in “groundless speculation.”