WASHINGTON -- The United States on Monday started to ease some of the economic sanctions on Iran after the Islamic republic has taken "concrete actions" in curbing its controversial nuclear program.

US Secretary of State John Kerry has approved waivers that offer limited sanction relief on Iran's oil exports, financial transactions and trade in gold and precious metals, among others, the State Department said.

The United States has taken the necessary steps to pause efforts to further reduce Iranian crude oil exports, allowing the six current customers of Iranian oil to maintain their purchases at current reduced levels for the six-month duration of an interim deal on Iran's nuclear program, the State Department said.

Washington is working with its partners and Tehran to establish financial channels to enable Iran to make payments for humanitarian transactions and medical expenses, university tuition payments for Iranian students studying abroad, and the payment of Iran's UN obligations, the State Department said in a statement.

The United States also took measures to suspend for the six- month duration sanctions on non-U.S. persons engaged in transactions related to Iran's petrochemical exports, certain trade in gold and precious metals with Iran, and the provision of goods and services to Iran's automotive sector.

In addition, the United States will license transactions for spare parts, inspections, and associated services necessary for safety of flight for certain Iranian aviation.

Monday's measures are taken in reciprocation for Iran's " concrete actions" to implement the interim deal reached in November between Iran and the P5+1 countries, namely the United States, Britain, France, Russia, China and Germany, the White House said.  

Iran has stopped producing 20 percent enriched uranium, disabled the configuration of the centrifuge cascades, begun diluting its existing stockpile of 20 percent enriched uranium, and not installed additional centrifuges at Natanz or Fordow, White House spokesman Jay Carney said, citing written verification from the International Atomic Energy Agency.

Iran's actions represent "an important step forward" in halting its nuclear program, Carney said  in a statement.

"Iran has begun to take concrete and verifiable steps to halt its nuclear program," State Department spokeswoman Jen Psaki said in a separate statement.

In exchange, the P5+1 countries and the European Union "will today follow through on our commitment to begin to provide the modest relief agreed to with Iran, Carney said.  

"At the same time, we will continue our aggressive enforcement of the sanctions measures that will remain in place throughout this six-month period," Carney added.