BRUSSELS (Reuters) - The United States intends to step up military operations against Islamic State in eastern Afghanistan during a temporary ceasefire between the Afghan government and the Taliban, senior U.S. officials said on Friday.

U.S. Army General John Nicholson, commander of Resolute Support forces and U.S. forces in Afghanistan, walks with Afghan officials during an official visit in Farah province, Afghanistan May 19, 2018. REUTERS/James Mackenzie

Afghan President Ashraf Ghani on Thursday announced the first unconditional ceasefire with the Taliban, coinciding with the end of the Muslim fasting month. The ceasefire excludes other militant groups such as Islamic State.

The Islamic State group has developed a stronghold in Nangarhar, on the porous eastern border with Pakistan and is among the country’s most dangerous militants since it appeared around 2015.

“(Operations against ISIS) will continue, in fact will be even intensified during this period of ceasefire,” U.S. Army General John Nicholson, commander of U.S. and international forces in Afghanistan, told reporters.

The ceasefire could free resources for operations against Islamic State but some would remain to monitor the Taliban and for force protection, he told journalists on the sidelines of a meeting of NATO defense ministers in Brussels.

U.S. Defense Secretary Jim Mattis said the United States could now redirect significant military capabilities towards Islamic State and other militant groups.

“If the Taliban take full advantage of the ceasefire in the best interests of the Afghan people, then many of the surveillance assets we (have) overhead could be reoriented to ISIS-K, to Al Qaeda and other foreign terrorists that have no business being in Afghanistan in the first place,” he told reporters. The regional branch of the militant group is often called Islamic State Khorasan (ISIS-K).

Afghan commandos, supported by U.S. Special forces and American and Afghan air power, have been carrying out an operation against the militants in Nangarhar.

The number of Islamic State fighters in Afghanistan is uncertain because they frequently switch allegiances, but the U.S. military estimates the number at about 2,000.

Before the start of a meeting on Islamic State militants, Mattis said the United States remained committed to fighting the militant group in Syria and any premature exit would be a “strategic blunder.”

“While we are nearing the defeat of the so-called physical caliphate in Iraq and Syria, terrorists operations elsewhere have increased... The U.S. remains committed to the conditions based approach,” Mattis added.

CEASEFIRE

The ceasefire announcement provides a potential moment of cautious optimism in the nearly 17-year-old war that has been defined by government corruption, weak security forces and militants that still control parts of the country.

The decision came after a meeting of Islamic clerics this week declared a fatwa, or ruling, against suicide bombings. One such bombing, claimed by Islamic State, killed 14 people at the entrance to the clerics’ peace tent in the capital Kabul.

Nicholson said the ceasefire was “significant” because it was the first of its kind. The Taliban has not yet reacted to the announcement. Mattis said it gave the Taliban an opportunity to end the fighting.

Privately, Western officials have expressed caution.

Michael Kugelman, with the Wilson Center think tank in Washington, said the ceasefire was largely symbolic.

“We should keep our expectations in check ... If anything, it will make the Taliban even stronger by giving it some breathing room and time to regroup and reload,” Kugelman said.

NATO’s chief Jens Stoltenberg said he expected allies to agree to fund Afghan security forces at the same level until 2024, despite public fatigue in Western countries about their involvement in the conflict. Funding has averaged at about $1 billion annually and Stoltenberg said he expected that level to be met.

In August, U.S. President Donald Trump unveiled a more hawkish military approach to Afghanistan, including a surge in air strikes to force the Taliban to the negotiating table.

Afghan security forces say the impact has been significant, but the Taliban roam large parts of the country and, with foreign troop levels of about 15,600, drawn swiftly down from 140,000 in 2014, there appears little hope of outright victory.

In another worrying sign, humanitarian organizations said nearly half of Afghan children are out of school due to conflict, poverty, child marriage and discrimination against girls, the number rising for the first time since 2002.

Nicholson also pointed the finger at Russia for providing “small scale support” to Taliban militants, adding that there had been an increase in such activity. He gave no details or evidence.