CIA drone missiles hit military targets in Pakistan for the first time in a month Sunday, killing four al-Qaeda members, but heightening tensions with Pakistan, according to the Washington Post.

Pakistan has demanded an apology from the U.S. for November airstrikes that killed 24 Pakistani soldiers. Until that apology comes, Pakistan has said it would not allow NATO convoys to cross into its territory. The Pentagon has said both sides are to blame, while the Obama administration has expressed regret.

Pakistan has provided critical supply routes for counter-terrorism efforts, while it gets billions in aid in return. Pakistan says the U.S. has not sent any payments since mid-2010. Negotiators have been working to reopen those routes as it becomes clear that bringing heavy vehicles cannot be brought over alternate routes in Central Asia without significant effort and expense.

The Post reports these drone strikes were not unexpected, but do cause tension between the countries.

“When a duly elected democratic Parliament says three times not to do this, and the U.S. keeps doing it, it undermines democracy,” a Pakistani government official, speaking on the condition of anonymity to preserve diplomatic relationships, told the Post. “These drone strikes may kill terrorists, but the net loser is freedom and democracy.”