Secretary of State Mike Pompeo says the U.S. is working to find a diplomatic outcome to tensions with Iran, which has been blamed for an attack on Saudi oil facilities, but he warned if diplomacy fails President Donald Trump “will make necessary decisions to achieve our objectives.”

Pompeo told the ABC News that the recent Trump administration decision to send additional U.S. air defense troops to Saudi Arabia  will “improve the capabilities” and “will make it more difficult” for Iran.  

Iranian President Hassan Rouhani said Sunday the presence of foreign forces in the Persian Gulf area would create “insecurity in the region.”

“Foreign forces can cause problems and insecurity for our people and for our region,” Rouhani said in a live broadcast on state television. The Iranian leader said he plans to present at the United Nations a regional cooperation plan for peace.

U.S. Defense Secretary Mark Esper said the American forces in the region would be “defensive in nature.” He added that the U.S. was responding to requests from Saudi and United Arab Emirates officials to improve their air and missile defenses after last weekend’s attacks on Saudi Arabian oil installations. U.S. officials have said Iran was responsible, an allegation that Tehran denies.

The September 14 assault exposed the vulnerability of the region’s oil facilities to drone and cruise missile attacks.

President Trump announced new sanctions against Iran’s national bank Friday, further escalating economic pressure on the Islamic Republic, but pulling back from any direct military action.

“I think the sanctions work,” Trump said Trump also said “the military would work, but that is a very severe form of winning.”

Secretary Pompeo said be believes Trump’s strategy on Iran is working.  

“We are well on our way to forcing the Iranian regime, to ultimately make the decision to become a normal nation — that’s all we’ve ever asked,” he told ABC News.

The United Nations has announced that it has sent a four-member team of international experts to Saudi Arabia to investigate the attacks on the oil installations.