WASHINGTON - U.S. Secretary of State Mike Pompeo is expected to announce Monday the Trump administration is ending sanctions waivers for those importing Iranian oil.

President Donald Trump reimposed sanctions on Iran last year after he abandoned the 2015 international agreement that gave Iran sanctions relief in exchange for it limiting its nuclear activity.

The sanctions are meant to pressure Tehran to change what the administration calls Iran's 'malign activities,' including its support of Syrian President Bashar al-Assad and Houthi rebels in Yemen.

The United States issued eight waivers when it brought back the sanctions in November, temporarily exempting most of the biggest buyers of Iranian oil. Those included China, India, Japan, South Korea, Taiwan, Turkey, Italy and Greece.

Since the sanctions were reintroduced, Italy, Greece and Taiwan have halted their Iranian oil imports.

It was not clear ahead of the announcement if the other countries would be required to end Iranian imports when the waivers expire May 2, or if they will be given more time to wind down their purchases before penalties take effect.

While the United States has withdrawn from the Iran nuclear deal, Iran and the other signatories -- Britain, China, France, Russia and Germany -- have said they remain committed to carrying out the agreement.

The International Atomic Energy Agency is in charge of monitoring Iran's compliance with terms such as limiting the number of centrifuges in operation at its nuclear facilities and abiding by caps on its stock of enriched uranium, and in multiple reports the IAEA says Iran is abiding by the deal.