The US is confident that Turkey's concerns over Finland and Sweden joining Nato can be addressed, a top White House official said on Wednesday.
Turkey's President Recep Tayyip Erdogan has voiced opposition to Finland and Sweden joining the military alliance.
Because all Nato countries must agree to any new member joining, Turkey could veto the memberships.
Turkey, the second-largest member of Nato, has criticised the Nordic nations’ hurried attempts to shore up their security by joining the alliance after Russia's invasion of Ukraine.
Turkey says their stance towards the PKK, a Kurdish militant political group, is unacceptable and is aggrieved over restrictions on military sales to Ankara.
But White House National Security Adviser Jake Sullivan seemed to downplay the risk of a Turkish veto.
"We're confident that at the end of the day, Finland and Sweden will have an effective and efficient accession process” to Nato and "that Turkey's concerns can be addressed", Mr Sullivan said.
"We feel very good about where this will track to," Mr Sullivan added.
He said Ankara was working with Sweden and Finland to reach a compromise.
"Finland and Sweden are working directly with Turkey to do this, but we're also talking to the Turks to try to help facilitate ... I expect these differences will be settled."
The two countries handed over their application documents to Nato Secretary General Jens Stoltenberg early on Wednesday in Brussels.
“I expect that Nato will speak with one voice and support of Finland and Sweden at the end of the day,” Mr Sullivan said.
US President Joe Biden also expressed his optimism that the matter would be settled through negotiations with Turkey.
“I think we’re going to be OK,” Mr Biden said on Wednesday.
In New York, US Secretary of State Antony Blinken met Turkish Foreign Minister Mevlut Cavusoglu and discussed the outstanding issues.
Mr Cavusoglu mentioned the PKK and defence exports as main hurdles.
“Turkey has been supporting the ‘open door’ policy of Nato even before this war," he said.
"But with regards to these possible candidates — or already candidate countries — we have also legitimate security concerns that they had been supporting terrorist organisations.
"And there are also export restrictions on defence products."
Sweden and Finland have in the past put export bans on some defence goods to Turkey.
“We understand their security concerns but Turkey’s security concerns should be also met,” Mr Cavusoglu said.
Mr Biden is meeting Swedish Prime Minister Magdalena Andersson and Finnish President Sauli Niinisto at the White House on Thursday, to try to shore up support for their Nato membership.