Barack Obama will receive a classified dossier in the next two weeks that will lay out the consequences for US foreign relations of the National Security Agency's powerful surveillance apparatus and provide the White House with a raft of possible reforms.

The document is being drafted by a top-level group of experts appointed by the president to conduct an external review of US surveillance capabilities and the damage to public trust resulting from the Edward Snowden disclosures.

The review, parts of which will be declassified and released to the public, will be completed by mid-December. However, a senior administration official familiar with the process said a secret "interim report" will be shared with the president shortly.

The group's work has been delayed slightly because of the recent US government shutdown, but it is expected to submit the report to the president via the director of national intelligence, James Clapper, in the week beginning 11 November.

The review is being carried out by a panel that includes Richard Clarke, a former White House counter-terrorism chief, and Michael Morell, the previous deputy director of the CIA.

Its importance has been amplified over the last week, after a series of revelations about the nature and scope of monitoring activities abroad, particularly against US allies.

On Monday, the US ambassador to Spain, James Costos, was summoned by the prime minister after reports in the El Mundo newspaper that the NSA had spied on 60 million phone calls in the country during one recent 30-day period.

The Spanish government called on the US to hand over all necessary information concerning "supposed eavesdropping carried out in Spain". Spain joins Brazil, Mexico, Germany and France on a list of countries demanding answers from the administration. On Monday, a delegation from the European parliament arrived in Washington to discuss the spy allegations with US lawmakers.

Last week the Guardian revealed that the NSA monitored the phone conversations of at least 35 world leaders. Separately, Angela Merkel called Obama to protest that her phone had been monitored, with Der Spiegel reporting on Sunday that the surveillance on the German chancellor began as early as 2002.

Asked about the reports on Monday, the White House's chief spokesman, Jay Carney, said the administration "acknowledged the tensions" caused by Snowden's disclosures. "We understand this has caused concern in countries that represent some of our closest relationships internationally," he said, "and we are working to allay those concerns and to discuss these issues."

"The president clearly feels strongly about making sure we are not just collecting information because we can, but because we should," Carney said. "We recognize there needs to be additional constraints on how we gather and use intelligence."

Jen Psaki, spokeswoman for the the State Department, which is managing the diplomatic fallout, added that the US was "not naive" about the impact of the disclosures on foreign relations.

The White House has declined to say whether Merkel's phone was monitored in the past. But according to the Wall Street Journal, the Obama administration ordered the NSA to cease the surveillance of her and other leaders after the program emerged over the summer in a separate, internal review of the agency's activities.

Carney said that internal review, led by the White House with input from agencies across government, will also also be completed before the end of the year. It contains what Carney described as a "separate" component dedicated to dealing with issues relating to "some of the very specific things with regard to intelligence gathered, including matters that deal with heads of states and other governments".

The external review, which will feed into the White House's internal assessment of surveillance, has itself been criticised for being too close to the Obama administration.

In addition to Clarke and Morell, the panel, which first met on 27 August, includes a law school professor, Geoffrey Stone, the former White House official Cass Sunstein and Peter Swire, who advised Obama and former president Bill Clinton on privacy.

The group has been tasked with reconsidering surveillance capabilities "in light of advancements in technology", seeking to find the right balance between national security interests and maintaining standards of privacy and civil liberties.

When he announced the review in early August, Obama specifically said it should consider "how surveillance impacts our foreign policy – particularly in an age when more and more information is becoming public".

The foreign policy component of its work has now provided a renewed focus. The extent of anger among foreign countries, particularly in Europe, has taken some administration officials by surprise. The most furious reaction has come from Germany, which is planning to send a delegation to Washington in the coming days.

The delegation is expected to include the directors of Germany's foreign and domestic intelligence services, who will expect to meet their counterparts, including the director of the NSA, General Keith Alexander, according to a source with knowledge of the trip.

The delegation, which will arrive late this week or early next, will also include high-ranking officials from Chancellor Merkel's office who will meet with counterparts on the White House's national security council.

Separately, a group of European Union parliamentarians arrived in Washington on Monday to meet with US lawmakers and senior national security officials and discuss what the White House called "privacy issues".

US representative Mike Rogers, a Republican, said afterward they discussed the need to rebuild trust and share intelligence.

Rogers, a staunch defender of US intelligence agencies, acknowledged the parliamentarians have brought legitimate concerns, according to Reuters.

"It's important to understand that we're going to have to have a policy discussion that is bigger than any individual intelligence agency of either Europe or the United States," he said.