US President Donald Trump and Saudi Arabia's Crown Prince Mohammed bin Salman held talks on Tuesday about Riyadh's role in Middle East stability, the need to maintain pressure on Iran and human rights issues. The White House said the two leaders, who spoke by phone, had "a productive conversation". Mr Trump has described Washington's relationship with Riyadh as important for the US economy and stability in the Middle East. On Monday, the US designated Iran's Revolutionary Guard Corps as a terrorist organisation, a move which aligned with Riyadh’s policy of countering Iran’s influence in the region. The White House said Mr Trump used the call with Crown Prince Mohammed to discuss ways of "maintaining maximum pressure against Iran". Saudi Arabia leads the coalition battling Iran-backed Houthi rebels in Yemen. Riyadh has accused Tehran of interfering in the kingdom's internal affairs and attempting to destabilise the region. Riyadh welcomed the move by the US to designate the IRGC as a terrorist group. The phone call came a day after the US State Department said it would deny entry to 16 Saudis it suspected of involvement in the killing of Jamal Khashoggi at Saudi Arabia's consulate in Istanbul. The list included Saud Al Qahtani, a former adviser to the crown prince who has been under investigation for his involvement in the killing. US Secretary of State Mike Pompeo has insisted that Washington will do what is necessary to punish those responsible. But the Trump administration continues to cite the importance of its strategic partnership with Saudi Arabia to the stability of the Middle East.