MURSITPINAR, Turkey — Turkey will allow Iraqi Kurdish forces, known as pesh merga, to cross its border with Syria to help fight militants from the group called the Islamic State who have besieged the Syrian town of Kobani for more than a month, the Turkish foreign minister announced Monday.

The decision represents an important shift by the Turkish government, which has angered Kurdish leaders and frustrated Washington for weeks by refusing to allow fighters or weapons to cross its border in support of the Kurdish fighters defending the town. Speaking at a news conference in Ankara, the Turkish foreign minister, Mevlut Cavusoglu, said that his government was “helping the pesh merga cross over to Kobani.”

The announcement, along with an American decision to use military aircraft to drop ammunition and small arms to resupply Kobani, reflected escalating international pressure to push back Islamic State militants. As the United States-led coalition has increased its airstrikes as well as its coordination with the Kurdish fighters, who have provided targeting information, the militants have lost momentum after appearing close to overrunning the town.

The battle has become a closely watched test for the Obama administration’s policy of combining air power with reliance on local forces on the ground to fight the militant group in Iraq and in Syria. At the same time, the American effort has been criticized — including by the Turks — as too selective and ineffective in stopping the suffering of other cities, under bombardment by the Syrian government or menaced by militants, in a war that has killed more than 200,000 Syrians.