The Senate is expected to approve a $625.8 billion defense budget by next Wednesday, setting the stage for a potentially confrontational conference with the House over ships, planes and funding for the war in Afghanistan.The House passed its version of the 2010 Defense Appropriations Act in July. Total spending is about the same, but there are some key differences in what the budget would buy.One is over how many C-17 cargo planes to buy. The Pentagon doesn’t want any, the House added $674 million to buy three and the Senate has allocated $2.5 billion to buy 10.Sen. John McCain, R-Ariz., attempted to strip the 10 C-17s from the Senate bill, arguing that the Air Force has more than enough large cargo planes and that the money the Senate would spend on more planes will force cuts in spending on wartime needs such as training, battlefield supplies and maintenance on equipment.But Sen. Daniel Inouye, D-Hawaii, said buying more C-17s is “a critical investment to support our national security strategy.”Sen. Christopher Bond, R-Mo., said that eliminating the C-17 buys would shut down the nation’s only large airlift production line and eliminate 30,000 jobs in 40 states. The U.S. might be “forced to turn to Europe or Russia for our future large airlift needs,” he said.McCain’s amendment to cut the C-17s was defeated 64-34.The House and Senate will also clash over whether to develop an alternate engine for the F-35 Joint Strike Fighter. The House wants it and added $560 million for the engine to its version of the Appropriations bill. The Senate followed the Pentagon’s lead and zeroed the second engine.House lawmakers argue that building the F-35 with only one engine option is risky — if an engine problem develops the entire fleet could be grounded, and an alternate engine could avoid that problem. Moreover, competition between engine builders could help hold down costs, they contend.The Pentagon argues the alternate engine is unnecessary and costly. President Barack Obama has threatened to veto a budget that includes money for an alternate F-35 engine.Shipbuilding is another area of dispute. The Senate wants to spend $3.65 billion on two DDG-51 destroyers in 2010. The House wants to buy one for $1.9 billion.On the other hand, the Senate wants to cut one Littoral Combat Ship (LCS) from the Pentagon’s request to buy three in 2010. Senators contend that the ship’s costs have increased too much to buy three for the $1.4 billion the Pentagon has requested.They also expressed concerns about construction schedules and the Navy’s future LCS acquisition strategy. They voted to spend $1 billion for two ships.The House went in the opposite direction. It boosted LCS spending to almost $2.2 billion and told the Navy to buy four ships.The House and Senate will also have to work out their differences over training funds for Afghan security forces. The Senate cut the Pentagon’s request by $900 million. That still leaves $6.6 billion, a 17 percent increase over 2009. Senators said they didn’t think the Pentagon could spend all of the money they requested for 2010.