WASHINGTON (Reuters) - The United States will resume admissions for refugees from 11 countries identified as presenting a high security risk, but with extra vetting for these mostly Middle Eastern and African nations, senior U.S. officials said on Monday.

U.S. Secretary of Homeland Security Kirstjen Nielsen testifies to the Senate Judiciary Committee on "Oversight of the U.S. Department of Homeland Security" on Capitol Hill in Washington, U.S., January 16, 2018. REUTERS/Joshua Roberts

The changes came after a 90-day review of refugee admissions from Egypt, Iran, Iraq, Libya, Mali, North Korea, Somalia, South Sudan, Sudan, Syria and Yemen by the State Department, Department of Homeland Security and intelligence agencies.

The new rules are the latest changes to the U.S. refugee program made by the administration of President Donald Trump to address what it sees as national security issues.

Some of the administration’s actions, including an executive order to temporarily ban all refugees, have sparked lengthy court battles. Refugee advocates have said they see the administration’s actions as intended to reduce the number of refugees, particularly those from Muslim countries.

During the review period, which lasted from late October to last week, admissions of refugees from those countries dropped sharply, according to a Reuters analysis of State Department data.

The changes announced on Monday include additional screening for certain people from the 11 countries, and a periodic review of a list of countries identified as presenting higher security risks.

The new guidelines were announced at a press briefing by senior administration officials, who spoke on condition of anonymity. They offered no details about which people from the 11 countries will be subject to the extra screening, citing security concerns.

The list of “high-risk” countries was last updated by the Obama administration in 2015, the senior administration officials said.

U.S. Department of Homeland Security Secretary Kirstjen Nielsen would like officials to factor in risks to the United States other than terrorism, such as transnational organized crime, a senior administration official said.

During the briefing, officials said refugees will not be barred from admission to the United States solely on the basis of nationality.

“The big picture is that there is no longer a refugee pause on countries, including the 11 high-risk countries, with these measures taking effect,” one senior administration official said in a briefing with reporters. “We’ll be resuming admissions with the new security measures in place.”

In an address at the Wilson Center on Monday morning, Nielsen spoke about the new security measures, saying they “seek to prevent the program from being exploited by terrorists, criminals and fraudsters.”

“These changes will not only improve security but importantly they will help us better assess legitimate refugees fleeing persecution,” she said.

Refugee advocates said they worry the new security measures will block refugees from the 11 countries from admission to the United States.

“Adding yet more hurdles to an already overly bureaucratic process will burden those seeking safety for themselves and their families,” Amnesty International USA said in a statement.

Since becoming U.S. president, Trump has imposed numerous limits on the refugee program, including capping the number of refugees allowed into the country in the 2018 fiscal year at less than half the number set by former President Barack Obama for 2017. He also issued an executive order pausing the refugee program pending a thorough review, instituted stricter vetting requirements and quit negotiations on a voluntary pact to deal with global migration.

For each of the last three years, refugees from the 11 countries made up more than 40 percent of U.S. admissions. But a Reuters review of State Department data shows that as the 90-day review went into effect, refugee admissions from the 11 countries plummeted.

Since Oct. 25, the day the 90-day review went into effect, 46 refugees from the 11 countries have been allowed into the United States, according to State Department data.