President Joe Biden will announce an end today to U.S. support for a grinding five-year Saudi-led military offensive in Yemen that has deepened human suffering in the Arabian peninsula’s poorest country, national security adviser Jake Sullivan said.

Biden sees the United States “playing a more active and engaged role” to end the war through diplomacy, Sullivan said at a White House briefing before Biden was set to speak at the State Department.

Today’s move, which fulfills a campaign pledge, would not affect any U.S. operations against the Yemen-based al Qaida in the Arabian Peninsula, or AQAP, group, Sullivan said.

Yemen, the biblical kingdom of Sheba, has one of the world’s oldest constantly occupied cities — the more than 2,000-year-old Sanaa — along with mud brick skyscrapers and hauntingly beautiful landscapes of steep, arid mountains. But decades of Yemeni misgovernment have worsened factional divisions and halted development, and years of conflict have now drawn in intervention by Saudi Arabia, the United Arab Emirates and Iran, which officials say has lent increasing support to Yemen’s Houthi faction of fighters.

The Obama administration in 2015 gave its approval to Saudi Arabia leading a cross-border air campaign targeting the Houthi rebels, who had seized Sanaa and other territory and were sporadically launching missiles into Saudi Arabia.

U.S. targeting assistance to Saudi Arabia’s command-and-control center was supposed to minimize civilian casualties in airstrikes. But Saudi-led strikes since then have killed numerous Yemeni civilians, including schoolboys on a bus and fishermen in their boats. Survivors display fragments showing the bombs to be American-made.

The Saudi-led campaign, joined primarily by the United Arab Emirates, another Gulf country, has only “perpetuated a civil war in Yemen” and “led to a humanitarian crisis,” Sullivan said. U.S. officials have already notified senior officials for those two countries to explain the rationale for the withdrawal of support, he said.

The stalled war has failed to dislodge the Houthis and is helping deepen hunger and poverty. International rights experts say both the Gulf countries and Houthis have committed severe rights abuses.

The weeks-old Biden administration has made clear that shifting its stance toward the Yemen war, and toward Saudi Arabia over the Yemen offensive and other rights abuses, was a priority. Other measures have included pausing some arm sales to Saudi Arabia and the United Arab Emirates and a review of the Trump administration’s categorization of the Houthis as a terror group. Critics say the designation hinders delivery of humanitarian aid to Yemenis.

Biden also is announcing the choice of Timothy Lenderking as special envoy to Yemen as soon as today afternoon when he speaks at the State Department. A person familiar with the matter confirmed the selection, speaking on condition of anonymity ahead of the announcement. The Gulf-based newspaper The National first reported the pick.

Lenderking has been a deputy assistant secretary of state in the agency’s Middle East section. A career foreign service member, he has served in Saudi Arabia, Kuwait and other countries in the Middle East and elsewhere.

While withdrawing support for Saudi offensive operations in Yemen, the Biden administration also says it intends to help the kingdom boost its defenses against any further attacks from Houthis or outside adversaries. The assurance is seen as part of an effort to persuade Saudi Arabia and other combatants to end the conflict overall.