U.S. senators John McCain and Dick Durbin, two of eight American senators visiting Ukraine this weekend, say they will urge U.S. President Barack Obama to immediately send arms and other military supplies to Ukraine’s government for defense against a broader invasion of the nation beyond the already Kremlin-occupied Crimean peninsula.

However, McCain and Durbin’s request met with resistance from another visiting U.S. senator, Chris Murphy, who said that Obama is right to carefully consider any decision to send weapons to Ukraine. McCain is a leading Republican and former presidential candidate, while Durbin and Murphy are Democrats.