The White House is working to put advanced anti-ship missiles in the hands of Ukrainian fighters to help defeat Russia's naval blockade, officials said, amid concerns more powerful weapons that could sink Russian warships would intensify the conflict.

Ukraine has made no secret it wants more advanced U.S. capabilities beyond its current inventory of artillery, Javelin and Stinger missiles and other arms. Kyiv's list, for example, includes missiles that could push the Russian navy away from its Black Sea ports, allowing the restart of shipments of grain and other agricultural products worldwide.

In addition to the fear of escalation, current and former U.S. officials and congressional sources have cited roadblocks to sending longer range, more powerful weapons to Ukraine such as lengthy training requirements, difficulties maintaining equipment or caution over U.S. weaponry being captured by Russian forces.