A senior Biden administration official said Monday the president would affirm the U.S. “commitment to Ukraine’s security, sovereignty and Euro-Atlantic aspirations”

as well as Ukraine’s efforts at government reform.

The leaders are expected to discuss increased collaboration on energy and climate issues.

For Mr. Zelensky, the meeting comes at a time of growing concerns in Kyiv about its relations with Washington.

Ukraine has been frustrated by the Biden administration’s decision not to block the construction of the Nord Stream 2 pipeline, which will supply Russian gas to Germany,

and by the lack of a U.S. commitment to future NATO membership for Ukraine.

Mr. Zelensky has also publicly expressed concerns about Mr. Biden’s June summit with Russian President Vladimir Putin, as Kyiv seeks more support from Washington

in its seven-year-old war with Moscow-backed separatists in the east.

“There’s a problem with Nord Stream 2, there’s a problem with NATO,” said a Ukrainian official close to Mr. Zelensky.

“We know the U.S. supports Ukraine, but we want tangible results.”

The U.S. withdrawal from Afghanistan has augmented concerns in Kyiv that Ukraine won’t be a focus for the Biden administration, the Ukrainian official said.

Ahead of the meeting, Mr. Zelensky emphasized the key role Washington plays for his country.

“For us, U.S. support for Ukraine’s territorial integrity, gaining NATO membership and joint opposition to Russian aggression are very important,” he said on Twitter on Tuesday.

Washington has long opposed the construction of Nord Stream 2, fearing Russia would use it to punish Ukraine by depriving it of the transit fees charged on Europe-bound Russian gas.

But the Biden administration waived sanctions on the project in May as it sought improved ties with Germany.

Mr. Zelensky has warned that Nord Stream 2 would mark a major victory for Moscow.

Kyiv has called on Washington to pressure Moscow to extend the current contract for transit of Russian gas via Ukraine, which expires in 2024.

Mr. Putin recently said Russia was ready to do so but was awaiting details on how much gas Europe would require.

Russia and Germany say Nord Stream 2 is a commercial project, providing a shorter and cheaper route for gas supplies.

In Ukraine’s east, meanwhile, Ukrainian forces and Russia-backed separatists have continued to skirmish, in a conflict that has killed more than 14,000 people since 2014.

Several Ukrainian soldiers were killed last month alone, the Ukrainian army has said.

Efforts to reach a political settlement have stalled.

Earlier this year, Ukraine also saw a buildup of Russian troops along its eastern border and in Crimea, the Ukrainian peninsula that Moscow annexed seven years ago.

Although Moscow soon said it had pulled back its troops, both Kyiv and Washington say the withdrawal has been limited.

Large-scale Russia-Belarus war games near Ukraine later this month are expected to further raise the temperature of the conflict.

The U.S. government has committed $2.5 billion to support the Ukrainian military since 2014, including $400 million this year.

Mr. Biden is expected to announce Wednesday a further $60 million security assistance package.

Amid the continuing confrontation with Russia, Ukraine has intensified its push for NATO membership,

but Mr. Biden in June said that Kyiv isn’t ready to join the alliance, citing pervasive corruption.