Crude oil futures were lower Tuesday as Gaza ceasefire negotiations appeared to stall and Israel vowed to launch an offensive against the southern city of Rafah.

The West Texas Intermediate contract for May delivery lost 26 cents, or 0.3%, to $86.17 a barrel. The June Brent futures contract slipped 12 cents, or 0.13%, to $90.26 a barrel.

Crude prices settled lower Monday after Israel reduced its forces in Gaza over the weekend, suggesting the country’s military campaign might transition to a more limited phase.

Oil rallied more than 4% last week as Israel and Iran teetered on the brink of a direct confrontation after Tehran’s consulate in Damascus was destroyed in a missile attack.

Israel Prime Minister Benjamin Netanyahu vowed late Monday to press on with an offensive against the southern city of Rafah on the Egyptian border, saying a date had been set for the operation.

“This victory requires entry into Rafah and the elimination of the terrorist battalions there.  It will happen —there is a date,” Netanyahu said in an address.

The U.S has warned Israel against launching an offensive against Rafah, where more than 1 million Palestinians who have fled fighting elsewhere in Gaza are taking refuge.

Ceasefire negotiations also appeared deadlocked in Cairo, with Hamas saying Israel’s proposal did not meet Palestinian demands.

WTI has gained 20.8% this year while Brent is up more than 17% as geopolitical tensions mount against the backdrop of a tightening crude supplies, with the market expected to enter a deficit in the second quarter.