Leaders are pushing to resolve disagreements on the eve of the NATO summit.

President Biden and other NATO leaders are making a last-minute push ahead of an annual summit to settle crucial disagreements that threaten to overshadow alliance unity in opposition to Russia's war in Ukraine.

The expansion of the North Atlantic Treaty Organization by adding Sweden and providing an avenue of accession to Ukraine is one of the thorniest issues.

On Sunday, Mr. Biden spoke with Turkish President Recep Tayyip Erdogan, who opposed the addition of Sweden to the alliance. Mr. Biden, according to the White House, told Mr. Erdogan of "his desire to welcome Sweden into NATO as soon as possible".

He there will be another effort to bring in Mr. Erdogan before the start of the two-day summit on Tuesday. NATO Secretary General Jens Stoltenberg is due to meet Erdogan and Swedish Prime Minister Ulf Kristersson on Monday.

Some NATO leaders also hope to approve a aimed at bringing Ukraine closer to the alliance, including the reaffirmation of a commitment to admit it into the alliance. Ukrainian President Volodymyr Zelensky - who is unsure whether he should travel to Vilnius, Lithuania, for the summit - told ABC News he would not go "for fun", claiming in an interview aired on Sunday that his country should obtain clear security guarantees.

But Mr Biden recently told CNN it was "premature" to start the process for Ukraine to join the alliance in the midst of war.

The NATO summit is the first to include Finland, which asked to join the alliance shortly after Russia invaded Ukraine last year. last. Finland became NATO's 31st member in April, doubling the alliance's border with Russia and adding a strong military with a long history of fighting the Kremlin.

Sweden's bid for membership has been blocked by Turkey's opposition, which has insisted that Sweden take a tougher line against pro-Kurdish activists and group members cleric that Turkey considers terrorists.

Here's what else to watch this week:

Biden visits Europe: Mr Biden arrived in Britain on Sunday for meetings with Prime Minister Rishi Sunak and King Charles III on Monday. After the NATO summit ends on Wednesday, Mr Biden will deliver a "meaningful speech" on issues including climate change and Russia's aggression in Ukraine. He will end his trip with a meeting in Helsinki with Finnish President Sauli Niinisto.

The end of the grain agreement is approaching: Russian officials threaten to let the agreement expire Black Sea Grains Agreement on July 17, accusing Western nations of not honoring the part of the deal that benefits Russia. The agreement allows Ukraine to ship agricultural products through Russian-controlled waters and allows Russia to sell certain products that had been blocked by sanctions. It has been extended three times, most recently in May, despite repeated threats by Russian officials to withdraw.